The celeb is the familar face, and look at the line ups the celebs are chosen not purely based on who is willing/had their arm twisted. Why do you think Eastenders, Casualty etc have always been well represented, they are popular shows and the public will know who Will, Patsy, whoever is.
Remember the debacle that was Series 1 with that muppet from Eastenders getting to the final when he could not dance at all, even after how ever many weeks it was training and practise from an expert. And that is one of the problems, the beeb want familiar faces but they would prefer them to be voted for on their performance not some fan basis or cos he/she is cute/got a cracking pair of.................. pins.
There is a reason why Come Dancing was axed originally and when they decided to try a Ballroom Dancing based competition the BBC had to give it some appeal to warrant prime time on a Saturday night.
Much as we like to think that we would all be here discussing Anton, Ian or Karen, if they had relied purely on the pros dancing then we wouldn't be on a third series. Maybe with the increased profile of the pro dancers there could be a series or at least a one off televised pro event, BUT that could only happen cos the celebs got involved in SCD and have made it a success.