Just seems out of place in a world where corporate regulation doesn't exist, makes me wonder if real world regulation stipulates that even in game advertisements need health warnings.

Quite a lot of the adverts have disclaimers or warnings in the small print.

Corporate regulation does exist, in fact it's one of the few things national governments still do. The issue is enforcement rather than absence; the megacorps are powerful enough that they can usually buy off any attempt to enforce legislation, or simply ensure the overly-inquisitive disappear.