No, that is not what happened. State governments initially did put into place age verification restrictions. Those restrictions were struck down by the Supreme

No, that is not what happened. State governments initially did put into place age verification restrictions. Those restrictions were struck down by the Supreme Court in Ashcroft v ACLU because SCOTUS believed that content filtering could be a suitable alternative. 20 years later, we know that content filtering is an abject failure. So the states are passing these laws to get before SCOTUS again to overturn Ashcroft v ACLU. The market never did this because they never had to before, and the internet has also drastically changed since this was first brought up.