Originally Posted by mushymanrob:
“nope, if you can sing, why mime.”
Probably because it's "safe." Speaking only for the artists with the giant voices (Celine, Mariah), they probably mime because people are expecting to hear a vocal that is nothing short of amazing, and they don't want to dissapoint. This is particulary heard performances of their more well known songs that their voice has changed since recording (Celine with My Heart Will Go On and Mariah with We Belong Together).
I can tolerate miming, but only if the circumstances are acceptable. A few examples would be Cheryl Cole because she does a lot of (good) dancing, and Mariah Carey because she's more than proved herself as a vocalist.
Some artists never mime, and I really respect them for that. Ke$ha, Miley Cyrus, or Pixie never mime (I think I recall Pixie doing it once and gave an interview afterwards, in which it was clear that she wasn't well).