Why can't Might Guy get his legs back? After the Fourth Great Ninja War, both Naruto and Sasuke lost an arm and Might Guy lost his legs (after awakening 8 gates). Tsunade and the team then built arms for Sasuke/Naruto using Hashirama cells.

Why didn't they chop Guy's legs and put Hashirama legs as well? Is it because Hashirama cells are not compatible?
Tsunade could not fix Guy’s legs because his body and his nerves were destroyed from fighting with Madara. Guy's body was really damaged and way worse than Sasuke and Naruto's damage.

There is a certain point where if it's reached, then there is no going back from it, plus the Uzumaki clan has special healing powers, for example Karin. 

But Sasuke on the other hand, didn't want to have his body healed, because it would feel like his sins are being forgiven with no consequences, especially after he did a lot of bad things to the Hidden Leaf Village.