Why Does My Kid Need to Put His Feet on Everything?

Yes, let it go.

My oldest was like this. He always had to be poking everything, and a few times he broke things because of it. It was really annoying at the time, but he really didn't mean to do it. He was always a kind of head-in-the-clouds kind of kid, and he just couldn't help it. Like you son, he was not trying to be naughty.

Now that he's grown, I regret the times I got mad at him about it. He was just a little boy with an undeveloped brain, and he really couldn't help it.

This too shall pass. One day you'll miss that silly little boy.

I will mention that you could issue a consequence for his behavior. I kind of feel like 6 yrs old is the beginning of "need to start listening" - especially since this behavior is unlikely to be accepted in school.

The consequence doesn't even have to be anything "bad" necessarily, but helping him to connect "gee, when mom says (or insert teacher or any other adult he should be listening to) keep my feet off of X, Y or Z, I guess she is serious." is really important.

I find it somewhat frustrating that many parents seem so unconcerned when their kids don't listen. It wasn't an option not to listen to mom or dad when I was a kid, why is it now? I wasn't beaten or spanked or bullied into it - but getting the message that listening to adults is really an important one and goes a long ways to helping our kids be successful later in life. If he doesn't learn on the small stuff that isn't as important, how in the world will he ever when it IS important - listening is a learned skill, not an innate one.

Good luck!

Lots of kids are just antsy and wiggly that way. It would be interesting to know if he does this at school and, if so, how the teacher handles it. Try using the same language at home as at school, which tells them it's a "universal rule" and not just Mom being a pain. Make sure Dad and babysitters use the same language too.

My reactions would be the following:
1) Stop commenting on it. I'm not sure that "Feet on the ground" is something you can enforce.
2) Remove books from the floor. If board games aren't being played, pick them up. "Since you're done playing and only want to step on it, we'll put it away." On some level, if it's his possession, it's his. If he ruins it, it's his loss. If you start with smaller things this way and a limited number of toys out at any one time, he'll see the loss of the toy/game more readily. He can also be involved in taking things to the trash can or the city dump and saying goodbye to them forever. The novelty of that will wear off soon.
3) Rungs of chairs: so, he'll fall and get hurt. He'll learn. Kids don't predict consequences (neither do teens, not very well). So sometimes they have to get hurt. As long as it's not life-threatening, it's not that big a deal. When my kid wanted to climb on the rock walls that are all over New England, I told my babysitter to just teach my son how to do it - how to test a rock first to see if it would wobble, and so on. They're going to do it anyway, so do your best to teach safety skills. Then let the bumps and bruises happen on a smaller scale long before the kid decides to climb on the neighbor's roof!
4) Breakables: put them away if they're yours. If they're his, let him break them, say, "Oh well, that's what happens when we step on things. Now it's gone. Poor you." And don't replace them.
5) Furniture: no shoes in the house, only clean socks and clean feet. See it as a positive - he's learning about his body, how far it extends, what things feel like with not just his hands but his feet as well.
6) If his feet are on other people, then leave the room or send him out until he can respect his personal space. If there's some furniture he can't do this on (like the good living room stuff vs. the playroom stuff), fine - have rules. "If you want to put your feet on the furniture, go to the X room which is the only room where this is allowed." That will help distinguish between what he can do at home (in some places) and what he cannot do at others' houses.
7) If bookshelves and dressers are not currently bolted to the wall, see that you take care of this. Too many kids are injured severely by tipping things over on themselves or on their siblings. Manufacturers make the right brackets, but hardware and baby supply stores also have things that adapt to other products.

If he has shoes on then start having him take them off when he's inside the house. We have a small bookshelf just inside the front door and shoes come go on here when they come off.

If he's doing it barefoot then has he stepped on a path of Legos? Perhaps he needs to have some pain when he's walking/standing on things to understand how it isn't safe?

Give him things to do with his feet.
I use to hold crayons with my toes - mostly to keep my sister from taking mine - but holding things and picking things up with my toes is something I can still do.
Comes in handy when I've dropped something and have no hands available to pick it up.
Give him a few hacky sacks and and teach him how to play.
https://en.wikipedia.org/wiki/Hacky_sack

HA!

My oldest still does this! She's done it for 8 years. No clue why or what need it serves.

I just gently remind her that feet belong on the floor. I'm hopeful (but doubtful) that she will out grow it.

I'm not sure that it would occur to me to try to stop it. Kids are little balls of enormous energy. I think asking him to stop is like asking him to go against his nature.

If it's a true safety issue, I would say something. But most of the time, if he were to fall it would be more like "ouch."

If there are toys or other things that can break, I would try to keep those off the floor. Other than that, I think you gotta let it go.

ETA - I absolutely agree with MilitaryMom that kids need to learn (and be expected to) listen. I just don't think feet on things is a battle worth fighting.

My feet are up on an adjacent chair as I type :)

One of my kids watched TV hanging upside down for a long time. Another one had to dismantle the couch while he watched because he liked making a fort.

Standing on things ... one of mine did that in preschool. He outgrew it. But yes, not even realizing he was standing on toys was odd - he genuinely didn't notice.

One of my kids throws the remote in the air when he watches TV. He's caught up in the program and has no clue he's doing it. I'll ask him to stop (I'm convinced it's going to go flying one of these days). He will stop for a minute, then start up again. Clueless. Doesn't fidget any other time. Can sit still for hours.

I would let it all go - except for standing on books, games, etc. Just remind him gently to put his toys away or off the ground. As you say, he's not doing it on purpose.

B., here's what I went through with my little guy. He had to crash into everything. He had to FEEL everything. I took him to an occupational therapist for an evaluation. It turned out that he had sensory integration issues, and he NEEDED to do this stuff. She worked with him for 6 months to help give him a "sensory diet" to retrain his nervous system to become more mature. It really helped.

An OT could give you exercises for him that give him ways to effectively use his feet in ways that give him what he is craving, other than all over your stuff.