They are not - much of the time, they use similar technique, they are just enhanced by the game environment.
It's not all pure endorphin though. For example, the game shows you that you can add up to three gems to get better rewards from some activity. When you go and buy those three gems and add them, the UI changes, showing you can actually add up to 10!
Or, all of the prices in the store are very carefully calculated so you have to buy more of the in-game currency than you actually need - an item you are likely to want may cost 20 gems, but you can only buy bundles of 17 or 39 gems, for example.
Sure, the endorphin rush is what makes you want the items to begin with, and there are aspects unique to the game design that encourage that. But there are a lot of other aspects of the game that are designed to confuse and convince players to spend more than they'd like.
You're totally right in your analysis. I'm not disagreeing with you at all about what these genuinely abominable games do, just the attribution of it. "Marketing" is a term of art; it means something.
It's not all pure endorphin though. For example, the game shows you that you can add up to three gems to get better rewards from some activity. When you go and buy those three gems and add them, the UI changes, showing you can actually add up to 10!
Or, all of the prices in the store are very carefully calculated so you have to buy more of the in-game currency than you actually need - an item you are likely to want may cost 20 gems, but you can only buy bundles of 17 or 39 gems, for example.
Sure, the endorphin rush is what makes you want the items to begin with, and there are aspects unique to the game design that encourage that. But there are a lot of other aspects of the game that are designed to confuse and convince players to spend more than they'd like.