IRL casinos at least have some oversight where they usually have to submit their design and algorithms to an oversight body. In Vegas, that's the Nevada Gaming Commission. So with a slot machine, you know that the odds are bad but at least they are fixed and deterministic.
With online gambling, it's just a black box. They can push an update and change things server-side, they can make the odds a function of the player, the time of day, the user's location... They are just trying to design the optimal Skinner box to separate a fool from his money. There are no regulations and no limits for an online gambling company operating in a legal gray zone outside the US.