Here in Norway there is official legal regulations that states that:
Children under the age of 10 should normally only be allowed to ride with a chair lift when they are accompanied by an adult in the same chair.
At the local resort we have 4-seat and 6-seat chairs. Instructor/coach to kid ratio is usually way less than that so to make things work it's needed that some of parents volunteer to help out. Happens both in ski club race training and in the resort ski school. Parents without a pass who help out get a vest and can ride the lift for free, but most people have season passes anyway since they are fairly cheap.
It can be a bit of a mess to have enough parents volunteering in our ski club race training. Sort out how many is needed when 0-50% of the kids doesn't show up without telling and to try to keep the responsibilities somehow distributed between the parents. We have a chaos-system
It doesn't end up being evenly distributed between parents, but most are OK with that. And it always works out in the end, even on those days when not nearly enough have volunteered beforehand
In total I think a chaos-volunteering works better for everyone than a rigid schedule that is forced upon the parents.
To me everything in US regarding safety seem to be so (overly)-regulated so kind of surprising that the chair riding rules seem more strict over here. But in the US system it might cause more headache to use untrained, uncertified and non-insured individuals to take responsibility for the safety of other peoples kids??? And with 2-seat chairs our way would completely break down....
Safety bars:
If you don't take the safety bar down they will stop the lift, go out and yell at you, and then go back in to start the lift again. If there is a queue, then the public humiliation that follows is very effective in ensuring that this doesn't happen very often ;-) Even effective on teenagers.