The difference is, nick, that no casino or sportsbook would ever want to say “but this is a game of skill”, because casinos and sportsbooks do not want skilled players!
(There are a couple of minor exceptions re sportsbooks, e.g. Pinnacle openly say they allow professional players. But most sportsbooks will ban you if they think you are a pro)
I did not suggest that there is no skill in either casinos or sports – casinos have bonus abusers, sportsbooks have arbers and knowledgable bettors, all of whom can make profits long-term. But no casino or sportsbook would ever want to admit that.