Did you not see the previous season w/ the same premise? Most of them try to wait until they can choose a match that they perceive to be in their favor. One other potential reason for people not wanting to go in right away is that the longer they stay, the more they get paid for being on the show(at least the veterans get paid like that according to numbers online sources). It's rare for anyone to be on the show that actually wants to "compete" these days and will take on anyone at anything. I wouldn't mind seeing a purely performance based version of the challenge, but that wouldn't make for as entertaining tv without all the voting drama and other bullshit.