They are just so triggered by the prospect of not picking up that precious piece of free loot fast enough when they leech Baal runs. It’s really all it is.
Edited:
I’ll expand on this to illustrate my point.
With Personal Loot, noobl33t165 joins game “baalzballz6736”. He/she gets the TP to the throne room. Sits in the corner and try’s really hard not to get hit by any straggler monster attacks during the minion fights. Once open, they all portal into Baals chamber, hide behind the pillars and do nothing, while one or two players actually do all of the work killing Baal. Then during the drop they don’t even have to make an attempt to be close enough to take any damage because they will get the loot for free anyway. They then exit and join “baalzballz6737” and repeat the process.
In the shared loot scenario, the player actually has to at least get close enough to some sort of danger so he/she has a chance to actually get some loot. That is the difference. Play the freaking game to get the loot.
It’s too easy to leech games in Diablo 2 by just following behind enough to not do any actual work. With personal loot, it makes it so much easier to sit back and do nothing while the people actually fighting who are close to the action, do all the work with very little reward, since that reward is now being distributed across all of the leeches. That is a bad thing.