> My initial thoughts are that poker such as TX hold 'em is not a game offered in a casino

Why not? Because you think it's a game where the casino can lose?

If so it's not an issue, as casinos that provide poker take "fees" from the stakes. Like how stock exchanges work: there are people making or losing money from stock market, but exchanges are always making profit.

Around where I live, about half the casinos offer poker and about half don't. Poker can be a pretty high cost to a casino. Compared to something like slot machines, it's financially mostly downside: You need a lot more physical space per player. You need more staff. In order for players to come and actually enjoy it, the poker room needs to be located in a relatively quiet corner, ideally enclosed so the buzz of the rest of the casino can't be heard, which is also expensive. And the game is slow, and rakes happen once per hand, so you're making money pretty slowly. And that's just for cash games. Tournaments are worse. If I had to guess, tournaments probably lose money for the casino, and they only exist to get players in so they play at the cash tables. Probably many other things that I'm forgetting because I don't run a casino.