Is there any reason why Zen Cart uses full URLs in its internal links?

the reason I ask is that I'm trying to cut the code down as much as possible, and reckon I can knock off another 12% if I can get rid of the full URLs and just use relative URLs... is there a way to configure the store to do that, or will I have to go through the template and edit all the files?

But I don't want to do it if there is a good reason for the full urls

Many thanks