Various reasons, one of them being able to avoid that type of problem that you just describe.
There are some people that queues in with little to no clue of exactly what to do in that current game that's expecting for someone to show them the way. Not everyone has the same experience. Can you really blame the pugs?
Either way, I'm still sticking with the issue being an adaption issue. What I mean is that there are options that hasn't been tried yet to deal with that type of group. It's hard to say in 72 man, because it's hard working with a big group whether you're premading or not. 24 man you have a bigger impact with how the game goes whether people know it or not.
Let's say, for example, that the bloodthirsty group is taking your base and is on their way to your spawn camp. Does anyone on your team have a Plan B or C to deal with this?