Man I was totally going to answer "Skinner box: Perhaps the same could be said of all RPGs" but you beat me to it
Anyway I am going to answer this.
The game limits the real-life time you're allowed to play it, like a mother that doesn't want you to play too many Vidcons.
So that means that the time you can spend playing is more precious than the time you're playing a regular game. This also means that when you're not playing despite having a full stamina bar, you are wasting precious playtime. Since the stamina bar gets fully charged every five hours this means you need to connect every five hours or you are essentially not playing as well as you could. If you don't play the game for a few days, you waste precious game time and maybe some events (just try doing it. You can't)
Hence the trap.
likewise if your mother limited your gametime to 30 minutes every day that cannot be stacked, you'd try playing every single day even if you didn't enjoy it that much
It's still cool though. I like traps.
Basically this plus what Grefter said.
Throw very, very, very addictive personality and you have someone starting new autobattles while waiting at stoplights and then sometimes while driving on empty stretches of road just to make sure my stamina bar didn't hit max and all of a sudden I catch myself waking up in the middle of the night because of some sound my cat made and go "oh before I go back to sleep I
should start another dungeon and blow my stamina." Emphasis on should, like it was a goddamn moral imperative.
Or during a lull in the conversation with some of my friends starting a new dungeon because I'm going to hit full stamina soon.
Or feeling relief when I check my phone and only have 6 stamina so I still have a while before I
have to play. All for a nostalgia trip through a franchise I honestly don't actually care all that much about and doesn't offer anything interesting in the way of plot or gameplay (or exploration but that is obvious)
Fuck that, and fuck these mobile games that prey on that tendency. Yes it is a personal failing that I fall for that shit but whatever, quitting altogether is easier than moderation so fuck that game.
At least with cookie clicker I couldn't fuckin take that thing everywhere with me.
EDIT: I also almost got very angry at whatever dungeon made you blow like 1 stamina per battle over 12 battles instead of 4 stamina over 3 battles because it made me have to pay more attention to that game to get the same amount done in my mind and no I am not doing that.