yes, I have known and seen many gamblers/bettors in my life and the vast majority have alot more control and "win more" or "lose less" with sports betting than casino action.
Maybe but a lot of that goes back to accessibility. It is pretty hard to bet sports in the US right now unless you really want to or are into it. Much easier to find a casino. So that is just a more likely way your avg degen will part with his money.
If it were easier then that might not be the case.
Letting people bet sports online could be like putting a casino on every street corner.