ah, fair, but with an easy enough fix. make data-enabled SIM cards be 18+ (or whatever age). show ID to the store clerk at purchase time, just like if you were buying smokes/alcohol.
just like you already are responsible for what happens on your free public network (torrenting, hacking, CSAM, etc.) in most jurisdictions
(for what its worth, i think age verification is dumb. but it looks like we're getting it one way or the other)