The thing you have to remember is that they are there for 21 days and there is less than an hour of time on TV. The editor snips tiny bits of this footage and assembless these into a show. Most of what happened will not make the final cut, more than one of the guests has said that they are not as lazy or stupid as they appear to be on the show.
Well if a guest wants to look good on the show, then he should keep his mouth shut, unless he ahs some thing nice to say, and get some cordage and make a fishing net out of that, or just look like you are doing that so you will always have something in your hands.