Cav missed the break in the Peloton, and once he was in that position, they would have needed quite a lot of the team to try and get him back to the front. At the end of the day, whilst winning stages is important, it's not as important to any team as keeping the Yellow Jersey, quite possibly until the end, so Cav lost out to Wiggins, quite rightly.
Cav is never likely to win the Yellow Jersey on The Tour, he's not really enough of a climber. Even if he has improved his performance on the hills, this Tour has shown that he's still not enough of an all rounder to keep the Yellow Jersey. Wiggins on the other hand, can, and the Yellow Jersey has a lot more credibility for advertising than individual stages, and at the end of the day, the team has to keep it's profile high, so that it's advertisers get coverage, since that's basically what they're paying for.
The Tour de France is a team sport. Whilst you need individuals who can independently do good things, and who can occasionally win stages or sprints independently of the team, generally you are very reliant on the other team members if you want to make a credible attempt on the GC.
I can also see Chris Froome moving on. If he does lead the team for the Vuelta, it'll be his chance to shine. If he does well enough, I suspect he'll be looking for another team to move onto very soon.