Same as every other game show on the box - every contestant has to have some "interesting" back story, anecdote or supposedly relevant reason for them taking part which the producers home in on. It stands to reason that therefore that you always get a bunch of egotistical, self-absorbed wannabees taking part.

That said, I love Traitors, one of the reason being that most of those on it who claim they'll be great at it because of their supposed inherent skills at reading and understanding people, get found out as clueless chancers.