In Annette's case I hardly think that was it. She was immensely famous, and remained so well after her Disney days. I think in this case it was just a matter of convenience. Not every song could be Tall Paul or Pineapple Princess. With the Sherman Brothers writing a big majority of your hits, you may have to settle for lesser work now and then. Here are a couple of very charming examples of our girl:
Annette with Bob Hope...so wonderful.
I wish I was one of these dancers.