After I had Nina, I needed a pap smear as I was overdue, and my dr checked for the usual things post baby.
After I had Emily, my dr only checked to see if my uterus had shrunk and asked the usual questions about b/f etc. There was no need for a pap smear or internal (thank god!).
So yeah, I think they're necessary. It gives you the opportunity to bring up any concerns with your health post baby, b/f matters etc.