A lot of games feature some element of randomness combined with betting. Examples being poker, roulette, loot crates (CS:GO) etc. Not that I would call poker or roulette real games. Or well, maybe card games can be seen as games, but roulette is just like the lottery. I do like card games, perhaps there should be more of them easily available for multiplayer online. I guess I could make a website app via Unity pretty easily, but the server would need to be hosted somewhere. I guess I could host it on my Raspberry PI now that I think of it. Card games are mostly turn-based and people don't notice if turn-based games lag at all. Apparently you can get some good ideas while you are writing. On the flip side, it would not bring in any money, but it would be a merit to have people play my games.
Should there be more gambling involved in games? GTA V had an update where they added a casino. Early on after this update, a lot of cheaters gathered millions or billions of GTA money from the casino since it was not made securely. I am not sure if they completely fixed that, but shortly after they also started banning people who were cheating using the casino. At least people have claimed to be banned. Unless you are cheating, there is not really much of a reason to gamble in GTA since you will just end up loosing money. Gambling could be done if you play against other players.