One reason why Plague's camp

Simple they don't use their pools until last minute. I don't see the point of saving face a strong team they might not use a single pool or face a experienced team they'll use the pools but when needed. I don't see the point of saving your pools they get used up and then you have to wait until you can infect another survivor but people can run a plague around fully infected for a while wasting time while there are pools ready to be used.