Public Servants or Egomaniacs?

I listen to all these people, many of them former presidential candidates, who say they would not accept the VP position under any cirstances. I'm forced to wonder if they just want "to be President" to serve their own egos. It seems to me that if you thought you had enough on the ball to be Prez, then you can still be of tremendous service as VP. Are all the candidates so egomaniacal? What ever happened to "Public Service"?