Umm, really. The problem is, your explanation didn't make much sense, and you also didn't make an actual argument for reinstalling. I'd be amazed if I heard one that was factual.
What do you mean by "factual?" If you don't believe the word of a person with a PhD in CS... do you mean like with references to an encylyopedia?
What doesn't make sense? Applications forgetting to remove temp files, disk fragmation, what?