Heard from @TeamYouTube about age retristricting the bath challenge video:
in short, kids might see it and repeat it and they don't want people to get hurt.
I don't want people to get hurt either so, sure. I'll deal with it.
Seems hypocritical and unfairly enforced. But OK.
It's basically the equivalent of an adult saying a child can't use a butter knife, in case they see someone attack someone else with a similar kind of knife. It's pointless, easily circumvented, and irresponsible.