I must admit, I can see why somone hosting files would perhaps prefer RAR to use less bandwidth, especially for lots of files, but certainly for myself, I never zip anything at all, and in fact don't even have winrar on any system in the house - I can't remember the last time I used it. I suspect for the majority of users it's simply not needed, regardless of it's functionality. It's quite easy to imagine people who download lots of stuff from the net very rarely coming across a RAR file, and wondering what on earth it is.