The other excuses are all just cope - little Timmy will just find a way around the blocks is true. Little Timmy can also get Heroin if he really wants or just one family might offer all the kids a hit on a crack pipe but it isn't an excuse to keep a needle, pipe and some fresh gear in the living room.
Block adult sites by default (much like a lot of phone companies already do) and the account owner can go in a make changes.
You only need one kid with a fake id that works, or for them to discover AI that can fake faces on a webcam to potentially expose all their friends...
Lazyness is a terrible excuse
I’m not arguing for either side, just pointing out a reality of the situation.
They’re going to use their parents’ devices, which are all age verified anyway.
More to the point: Age block technologies have been around since the mid 90’s and, for thirty years, parents have voted with their wallets and not installed them. In areas where they’re free, parents still don’t want them.