Running a casino is a business, so it's doesn't even make any sense to suggest this as an option when it comes to relying on something gambling related for survival, owning a casino is business, a lucrative one for that matter, most especially if well managed and marketed, it can turn out to be the source of financial breakthrough for the owner, no longer about just looking for something to rely on for survival.
And going back to gambling, I agree with all that you have said, but not with some form of exceptions though, it's really hard or difficult to rely on gambling for income, but it's not absolutely impossible, and regardless of what data or studies shows or says, there are still people around the world that having nothing else doing aside from gambling, doing sports betting and so on, and some seem to be making money off it though not without some loses from time to time.
The thing is, level of luck differs for all humans, there are people out there who are highly favored with the ability to easily win games through gambling, and its not impossible for such people to make a living off gambling.
Sports betting is very different than gambling games. People relying on gambling games to earn an income from them are doing it wrong because it's technically not possible for someone to be earning a constant income from gambling games considering the fact that the results are completely influenced by luck and a person can't possibly be lucky all the time. You may win $50 today but you can lose $100 tomorrow, so the $50 you won yesterday won't count anymore since you are at a loss of $50 today.
When it comes to sports betting, it is something that you can do if you have a lot of knowledge and experience about a specific sport or multiple sports and have also have experience about the game yourself and you understand how things basically work. You can't make money from sports betting either if you are making guesses without having proper knowledge.