That has nothing to do with the point being made. The point was about to what level parents are responsible for things they allow their kids to do, regardless of how "addictive" it is. Particularly if they know it's harmful.
I'm not saying that parents don't have any responsibility, but it's about practicalities. If a teenager can easily buy smokes or alcohol, many will, no matter what the parents say. If you make the goods harder to buy, usage drops. So, shops / software vendors do have some responsibility for societal outcomes.
In a libertarian utopia, anything goes, but kids are... weird in that they often try to push the boundaries of their autonomy without always knowing the risk, and it's in our collective best interest not to let them go too far.
I'd argue most adults are just oversized kids in a trenchcoat