Dude... Wilder lost his title, and the closest opportunity to getting it back is via this rematch. No sane boxer would miss this kind of opportunity, no matter how outclassed they were.
If Wilder loses again in the 3rd fight, I don't think he would wear the "champ" belt for quite some time since Fury would move to the next opponent.
I have the same perspective, if Wilder has any desire to be a champion again then he will need to take the rematch fight immediately, even if he losses the next fight as well he has something to prove, he was completely dominated during this fight, he only put up mild resistance during the first two rounds and from there everything was about Fury, he at least needs to show he can present opposition to Fury or whatever legacy he wanted to create will go down the drain, and if he avoids the fight then the natural fight that will follow will be Fury vs Joshua and he will probably have to wait for years for another shot.