I have five kids. The oldest two have friends that have various devices. But I don't care about their friends and don't cave. Believe me, it's really not that hard. Kids whine about all sorts of things, just add wanting a smart phone to that list. As an added bonus they get a lesson in not giving in to social pressure.
Parents parenting is the only way to solve this problem. And yes, some parents aren't going to do a good job parenting. It's the same with tobacco, drugs, alcohol, or any other dangerous behavior. I honestly can't wrap my mind around how people think regulation is going to do that job for them. No amount of regulation outside of an outright ban is going to make this go away. Sure, some guardrails can help, but at the end of the day people have to be taught how to avoid bad behavior on their own.