Is this wheel a bit too much for a cage this big?

Only two of my pet rats actually use the wheel, but all of them get a good 1-5 hours of outside the cage time so Im wondering if its really necessary to keep it in there. Looking at the photos you can tell which rat never uses it.. (hint its the fat white rat.. but when he's out he gets tons of exercise)

I'm just curious because the cage seems to be quite crowded.

Here are a few photos