IE recently gained in popularity or usage or something I think... so yeah, people use IE. Not everybody is technical minded, with a few not even aware that other options like Firefox and Chrome exist because most people buy the Windows platform that has Explorer pre-installed on it (and the same for Mac and Safari I'm guessing?)
I use it, don't really see much difference regarding performance between browsers because with Internet like mine, everything's crap at the moment. Unless if one browser starts magically giving me 1,000,000 MB/s download speeds, they're all virtually the same to me, bar a few compatibility issues with code.
Also, yay Wikipedia!
http://en.wikipedia.org/wiki/Browser_wars