This is equal to: "Why don't casinos run out of business?", or "Why can't you win long term from gambling?" , and most important "Why should you consider gambling just a means of having fun, and not a job?".
Well, for starters, let's take roulette, which is my personal favorite. Afterwards, we can generalize and extend the idea to all the games that involve gambling at a casino.
As you know, European Roulette offers you the best chances to win, because it has only one 0 (zero). In this case, the odds for you to win a, let's say, even bet are 48,6% , and pays out 1 to 1. That means your bet is 50% of the winning. So the chances for you to actually win the bet are smaller than the odds of loosing. This means that, if it were for the casinos to be fair, you should be paid 1.15 to 1. However, this is not the case. The difference is not major, you might say, but because this difference you can NOT win long term in a casino, even if you are lucky, you will eventually run out of all your luck, and thus, the casino will collect all of your loot. Game Over!
This is valid for all other types of bets. Here is a table of odds to win and actual payouts. You can notice that all the payouts are smaller than they should be if it were to be fair.
And for American Roulette the odds are even lower, but the payouts stay the same. So now you know why casinos don't get bankrupt. Unless you figure out a way of predicting the outcome, without being detected by security, which is kind of hard, if not impossible.
The same happens in all casino games, but not only. The Lottery is also based on the same principle. Keep the payouts lower than the actual deserved payout, given the odds for that outcome=Profit $$$.
So there is no reason in lying to yourself that you can beat the system. Maybe in the short run you will, but in the long run, you always lose. And you lose more than you have recently won. This is kind of the first law for casinos. Make people believe at the beginning that they have a fair chance of winning, and then collect all their money they've spent dreaming for that new car, or house, depending on each others interests.
Good luck! And may you wisely spend your money!