Because addictive things are addictive, and addicted people suffer, and everyone can get addicted if their guard slips.
We prefer to regulate highly addictive things instead.
Yes, since more people use Tiktok than not. The average person is also fat today, so this shouldn't come as a surprise to you.
People didn't grow fat and addicted to screens due to changes to themselves, its due to companies learning how to get people to eat more and watch more since the they make more money.