A lot of people just can't cope with the completely normal interest in sex that starts at puberty, and they want to bend the world backwards to pretend that this is a switch that flips on people's heads exactly at 18. I get that it's a complicated matter to handle, but it's also a fact of life.
There are right and wrong ways to protect kids and teens, but banning tits is just a display to appease parents who don't really want to think about it. If they did care about their well-being they'd focus on being more watchful towards creeps in online platforms rather than policing raunchy fictional content and convincing themselves teens aren't figuring out how to get it anyway, as they always have.
Meanwhile gambling for children makes a lot of money, so why would they care about the psychological issues that it causes on developing brains.