I will jump in here to say that I do the same thing vkaryl does, mainly though as a way to make sure my backup copies of my sites (which are kept on my hard drives) are the same as the one on the server. Plus, I always save a copy of any of the zip files of any plugin/theme/etc in case I need to go get a fresh file when... um... IF I screw something up, without having to hunt it down again.
I've got shell access, and once upon a time I knew how to do everything there, but I've long since forgotten a lot of what I used to know. Everytime I go into vi these days I stop and get a glazed look for a few minutes while I try to recall vi commands.
But to the point - let me just echo what everyone else has said. Actually, you're lucky if most of the users out there even know how to unzip and FTP. No, I'm not kidding. With the proliferation of Fantastico/one clicks, a lot of people have websites and blogs who have never touched FTP, and having done tech support for many years, I can tell you that zip is still an unknown to a lot of people.
Not that I'm suggesting you try to be that in depth - just making the point. :)