^^Why? Other Federation ships in the AQ got in space battles and appeared the same way in the next episode. Voyager had the same technology at their disposal, so that argument doesn't wash. I suppose one could make the case that they didn't have the same external resources, and yes, Voyager didn't have any Starbases nearby to fuel up...BUT, like Exodus said, after a few years, you'd have gotten the survival part down well enough to be prepared for such matters. I'm sure Voyager ran across a few friendly ports where they could restock/salvage/barter and meet their needs.
The show really wasn't meant to be like nuBSG--for one, the Federation's technology exceeds that of the Colonial's, hence Voyager's ability to look and fare better than Galactica--it's about maintaining one's Federation values in less than friendly territories. That's why Voyager had the look and feel of a Federation ship.