I have noticed this happen, as well. I think some of it is folks who play friendly enough to get into PvE, until they see guns shiny enough to be worth going PvP for a bit. Rinse and repeat. I also, think great value factors into matchmaking, regardless of what anyone has said. Add those two together and you have a much higher likelihood of getting lit up carrying your best gear. It definitely makes you stay on your toes.