Well some premade team want to compete against strong player, however; some just want to gank PUG to help their members or enjoying easy win. Every WZ win earn you at least 100 WZ com, and each last for 15 min at least, do the math.
Going by this thread
http://www.swtor.com/community/showthread.php?t=554133 most PvPers don't want to play against someone better than themselves.