I doubt it's going to be as widespread as people estimate, but I think it makes perfect sense regarding the "age appropriate" ways kids are allowed to act these days which has gotten way out of hand. Our kids are well disciplined, but we get incredulous compliments all the time because people are shocked they can actually act...well...to us...nice and normal. IMO the new trend is probably behavior related, not just a sudden unfounded dislike of young humans.
Regarding airlines, the last few flights I've been on, older kids have been tantrumming for large stretches of the flight. TANTRUMMING, and ordering their parents to non stop walk them in the aisles. The flight attendants couldn't even work. We're talking "speaking" age, 3 and up, not babies with ear drums hurting, not even two year olds who can't be expected to behave the whole time, we're talking bratty kids making the whole flight stressful while their parents comfort them and cave to their commands and walk around the whole flight. Why is this suddenly OK for society where people are trying to function and conduct business? You know how hard that is to sit through on a flight, picture being an attendant dealing with it constantly? Some attendants are saints and parents themselves, but not EVERYONE can be expected to have nerves of steel.
Same in restaurants. My husband and I are blown away watching parents amble around with their kids in the way of the staff because they can't sit in a chair for 45 minutes and eat, or letting them bother adjacent booths and fuss the whole time. Parents can't expect their kids to act disruptively and still be accepted by everyone in public.
For centuries everyone has been understanding of emergencies and occasional outbursts from kids, even in the 70's, my brother and I were never allowed to act that way, but OCCASIONALLY we'd see other kids do it (and the parents would often get and earful from other parents) but nowadays, it really is disruptive behavior allowed on a large scale.
If society's standards go down, then they cant' blame businesses for reflecting that. I think it's a great opportunity for new places to become refuges away from kids for an adult set. Most of my adult friends have no kids and HATE kids around when they're out. For good reason. We sense eye rolls when we bring kids into pubs (for good reason since the people are probably trying to escape kids), but once we're tucked into our booth bothering no one, we start befriending people.
My only worry is that we usually take the kids to adult places where no kids are, so hopefully that won't have to stop, because we hate kid friendly restaurants. But if that happens, I totally understand. It's sad for the kids who do behave though.
Businesses would lose money by losing families and sales (which is why I don't think it will get too wide spread), so for the ones that do it, it must be worth it to them to not deal with the kids, or they must know there is a clientele out there that would appreciate it.