...because it deserves it!
I've been playing this game since 11.12.2011 and it does not seem to end. Well, technically I could finish it already if I wanted to; I could always play the main quest only and just go through the story. But there's just so much to see and do in the game, that you would just be ruining it for yourself if you go "save the world" already.
Another thing I don't understand about most Skyrim commentaries is how some people would enchant and smith super items and breeze through the thing. You're ruining it for yourselves!