Wasting time.
The classic models were very low poly and the textures very low resolution, really I don't see the point in creating a carbon-copy, considering the originals were only like that because of the restraints of the technology of the time.
Even though they're low in detail, they would still take an unreasonable effort to make and would for the most part be taken for granted and would also possibly fail to recapture as much nostalgia as you would like.
Imagine yourself playing on ge_library right now, but with original textures... blurred, smudged, undefined... Personally I'd get sick of that pretty fast, especially knowing how crisp and fresh things can look with high resolution textures. I'm sure I would be just as irked playing with blocky low res characters and weapons.