about 4 years ago - Shurenai - Direct link
The truth is you'll hear a thousand different stories from a thousand different people.

The game is made for co-op, almost entirely- It's built with it in mind from the ground up. It's very well suited to every player taking on one aspect of what needs doing, of sharing items for the benefit of the whole, For being Cooperative.

But some people don't like that the game multiplies gamestage (the method of measuring zombie difficulty among other things) when in a coop party. Mostly because they don't understand just how much easier everything gets when people team up in co-op; The slight increase in difficulty is meant to counteract how much easier it is to get everything done.

Theres other reasons peeps might not like it, but, as i said above, the games made for coop from the start, and in my personal opinion, Coop with friends is a great way to play; possibly the best even if you and your friends get on well and don't get all selfish n stuff. :P