They actually DO talk about having their allies taken out is a loss to them. Sure, it's played off as an inconvenience, but it's only an inconvenience because the next part of the plan can proceed without them. The idea is that the Team needs to erode the power base of the villains before they can finish them off. It's partially the foundation of the ongoing struggle aspect of the show. the other part is the "knowledge is power" aspect. The Team doesn't know who the members of the Light are, or where they're working out of.