To me, taking the cart and pushing it into the console is all a part of the experience. Holding it in my hand and feeling it with my fingers. Having the hardcopy also gives me the feeling that I own the game. It's mine. I feel that way about carts more so than I do about discs. I am kind of queasy when it comes to any of the CD based units. I feel that when they die at some point, it is over. Where as the carts have clones, even though they are so iffy.
I know that space is a problem, I know that all to well. I just like sometimes looking through my collection. Just having it in front of me gives me the mood, and I think, hey I haven't played this in a while.