Do parents do this for extended periods? I notice my brother and his wife being far more disciplinarian and continually trying to calm them. I understand that, but does anybody go the other way and try and encourage more of the chaos and imagination?
The kids are 6 and 8.
There are methods like Montessori that try a more hands-off approach and let kids be kids. Other cultures, like Japan (https://en.wikipedia.org/wiki/Old_Enough!) give kids real responsibilities at a much younger age, letting them apply that practice.
I will say that in the defense of your brother, parents are often stricter with kids in front of other people. If they never discipline them, then they won't follow rules. You don't want to be the parent whose kids run around and scream at the restaurant.
At the end of the day, its balancing act. Letting them run free turns them into little monsters, but strict discipline only turns them into a different kind of monster.
We try to do lots of imagination play when we can, especially when we play TTRPGs, or on long drives together. It gets harder as the kids grow older, because they have different wants, and different friends, and then they make different schedules, and so on.
(And pretty soon they are randomly saying stuff like, "I saw something funny on Reddit today" in a voice that sounds at least an octave deeper than you remember, and you realize you might as well hand over your car keys now, or that your last debate on Reddit may have been with your kid or their tbh-pretty-annoying friend)
Still, we are doing cyberpunk TTRPG play recently, and my son--er, "Slag Cypher, Assassin for Hire" is super into it, sister has committed to play, and I've _almost_ got their older brother interested. Other than that we have some long-form campaigns going since about 2018 in other genres. They remember their gear, pets, etc. wayyyy better than I do. "Don't I have a pet spider that could bite the guards?" Damn, OK.
All it really takes is a bag of dice, basic understanding of probability, something to draw maps on or one of those cool map books [1], and let them bring their own minifig / character. Look up "{genre} ambience" on Youtube, hit play and you're g2g.
Still, if parents aren't into this I wouldn't push it too hard. Imaginary play activities are 100% OK for kids to really discover on their own later, and pushing perspectives that are...non-native to the parents can raise the parents' stress, which in turn can spur some unwanted outcomes at home.
A lot of parents would at the very least need to see it structured and treat it more as a workshoppable activity than something that comes naturally to some and which therefore should be comfortable from the get-go to them...totally fair IMO.
1. https://www.amazon.com/Giant-Book-Sci-Fi-Battle-Mats/dp/B084...
But, if you can give then some some time and space, this is the one of the best parts of being a parent or trusted adult.
We had space so I was strict about rules about e.g. meals, bedtime etc but outside that they were allowed a lot of freedom to go wild with the chaos and imagination and it was some of the most fun I have ever had.