Addiction is a neuropsychological disorder characterized by a persistent and intense urge to use a drug or engage in a behaviour that produces natural reward, despite substantial harm and other negative consequences.
If you employ psychologists and other specialists to design something for maximum retention, you‘re not making something „entertaining“, you‘re tricking the brain into a loop.
We could discuss this endlessly but suffice it to say that there are techniques for retention that dont make an experience necessarily better but more captivating. Infinite scrolling is a very simple example. i bet some game designers could shine a pretty bright light on this if they stumble across this thread.
I could abstract this to the real world like so: two people can speak exactly the same text but one cares if their audience is getting tired and stops, the other one speaks a little louder and turns on some more lights. I‘m pretty sure you will get a significantly longer retention despite the quality being the exact same.
And this is why methods for retention need to be carefully screened and regulated.