If phones were somehow rated M for mature or something and parents had to be with their child for purchase and there was similar messaging as to with smoking or drinking or video game violence PSAs, I think we'd be in a different place. I bought my own phones with my own money as a kid, not as young as 13, but definitely underage. If my parents thought it was going to lead to the kind of harm people are positing kids are being exposed to now, they would not have allowed much less accompanied me to get one if that was required.

If they're doing this because they think unrestricted phone access is as harmful as they think violent games or alcohol or smoking are, then it makes sense they want to similarly restrict phone access for children. Phones don't have as robust a child protection infrastructure as a lot of parents want, or the way to implement it currently is too difficult for parents to understand. I'm not saying this needs to be done, or makes sense, but companies regularly are expected to comply with child protection laws. That's why no matter what, certain medications come with child resistant packaging. They don't care if you have a child or if there's any way a child could get access, they assume it and add that protection in. I don't think pharmacists or doctors are giving kids drugs directly, and yet the childproof caps are still a thing we all have to deal with. You initially suggested that companies are not responsible for child safety, but obviously they have been previously. These are compromises we make as a society. I'm not saying they are good, just that it's already a thing.