It's because it's addictive, and we live in a capitalist free society. Bad things can be stimulating, fun, and addictive, and so people will still partake in th

It's because it's addictive, and we live in a capitalist free society. Bad things can be stimulating, fun, and addictive, and so people will still partake in those things to their own deficit. We can't just ban things because they have negative consequences, cigarettes literally kill people and they're still in every corner store, but this is especially an issue when it comes to mediums for free speech. The companies responsible have no incentive to prevent harm, because what they are doing is profitable. The more addictive their product is, the more money they make.