Probably because Nick is still working on getting back into fighting shape. Nate currently is still a main event fighter, his ppv numbers makes him that way. His last loss is to a doctor stoppage from a cut, so he still has leverage and he is smartly using it. There's few fighters that move the needle with PPVs, Nate is one of them. Nick probably doesn't expect to be the main event in his come back fight. I think he just wants to make sure he is actually fight ready. He has been drinking every weekday/weekend for the past few years. He definitely wasn't in fighting shape and wasn't taking his training seriously during that time.
the last 4 or 5 years someone from team nick diva always says he in the gym never looking better fight news soon. how is nate using it smartly. he turned down the jorge rematch when he said it all he wantd. he not looking to fight dustin any mroe after getting all twitter but hurt. nate knows he can use his twitter thumbs more to get clicks and attention than fighting which now looks like taht all he cares about now.