One can compare the photorealist schools of painting. It's possible to paint so that the result looks like a photo, but most artists don't try, even if they could achieve it. The argument goes, why bother? If you want a photo, take a photo. Using a hi-res photo-based texture is a bit like loading a 2D plane into Poser, texturing it with a photo of someone, and rendering it. The result is a Poser render and it's photo-realistic. The big deal. Actually I may try that sometime :)