If you shoot JPEG, you can't adjust the exposure, white balance, noise reduction, or sharpening without degrading the image. Even if you use a nondestructive process on the JPEG image, you're still performing noise reduction and sharpening on top of the camera's NR and sharpening and on an image with a compressed color gamut and tonal range. You may not care now, but you might in the future. For instance, I shot this at ISO 25600 with the Canon EOS 5D Mark II, which was state-of-the-art for high-ISO-sensitivity shooting when it first came out. Now, software noise-reduction algorithms can do a better job than was possible in-camera at the time (this was processed with Adobe Camera Raw 6.6 beta). I hope that soon software will be able to help me do a better job fixing the white balance in this photo.
Furthermore, when shooting candids, there's no guarantee you're going to get it right the first time. Raw is a safety net.
(Christmas 2008, 1/125 sec, f5.0, ISO 25600, white balance adjusted in software, Canon EOS 5D Mark II, 24-70mm f2.8L lens)