When they're ready and mature enough and can do it then potty training is super easy. So many parents take it as an affront when their child isn't trained at 1 or 2. It's supposed to be natural and pretty easy.
A toddler doesn't really have the ability to HOLD it for very long. That's when potty training is the next step. Kids can be aware of the feelings in their bladder and that there's pee coming out and such early on but the actual cognitive brain function they need to have to not even know they have to go but hold it anyway, then acknowledge they need to go when they feel that urge, make the trip to the bathroom, pulls stuff down, get on the seat, go, wipe, pull stuff up, go wash hands, etc...that's brain stuff.
I will tell you that I didn't even have a kid's bathroom in my toddler room in child care. I had one in the 2 year old preschool classroom because that's usually the oldest any of the kids will be mentally ready to get the whole thing. AND I required pull ups for anyone not in a diaper full time. Why? I didn't want to hire a janitor to run around that classroom all day cleaning up pee and pooh off the flooring and furniture and cots and toys and picking up play clothes and stuff to run it off to the washing machine.
Having a potty training child in panties is nasty. I know, you can clean it up and it not be nasty. But it's still hard to get every single spot. Pull ups keep it clean.
By the time the kids were turning 3 and getting ready to start Head Start they had to be potty trained. We really focused on that older 2 year old and the 3 year olds. They are usually ready.