The is what is always over looked about campers. You say they don't get lots of kills. I say they don't get lots of deaths. Most good campers finish the match with something like 7/2 or 10/3. That's a +5 and +7 meaning they actually helped the team more than a shaggy who gets 17/15 or 17/19. Most shaggies have a negative K/D ratio which in a game like COD, ends up hurting their team WAY more than helping it since there's a short time limit.
Overall, camping is a better strategy.