well for one, theres nothing to do in d2 until shadowkeep, and a 30 hr campain only takes 2 weeks of playing 2 hrs a day, not including more on weekends. And for 2 not everyone is going to go into bl3 and do the campain 4 times. if i do more than one playthrough it'll probably be when i have little or nothing to do after a few weeks of shadowkeep.