why casino is always profitable bcoz most people will lose and that is a true 
Casino's are always profitable even if somebody wins because the way casino plays they will let someone win and the other lose but their are plenty times for the losing part, and casino's tend to let you will at first but will let you lose on the end.
Casinos are not afraid of you winning their money but they are more afraid of you not betting with them. When you bet more often, you have a higher chance to lose with the house edge. This is one of the reason why casinos give you freebies to encourage you to return to bet.
Yes freebies are to induce the gambling addictions. I do see many people are making good profits in demo accounts and failing in real gambling. Same way when you bet in small amount you will win. When you go with bigger bet amount, no other go other than loss. Long run is just a theoretical, even in short run I faced losses.
What theory is that? I dont think that is possible thing, the only thing that cause of your loss because you dont have enough balance to cover your loss so in the end you are lose all of your bet. Although it is a long run but if you can maintain your balance until the end I think you can cover your loss and get some profit