Those figures
do not show what people think, only what they're using... and I question their accuracy. 19% seems awfully low for Firefox.
Browser Statistics
Firefox global market share reaches 21.1% - Mozilla Links
Firefox share up over 20% in Europe, mostly at expense of IE
Obviously from Firefox themselves, "gilding the lily"
You've got to keep in mind that you're average computer user isn't going to spend a lot of effort testing out different browsers to find which one is best or which one they like most; they're just going to use what's there. It's not until the good son comes home and cleans up Mom's PC that she stars using a more reliable browser.
You know, MS lost a big ol anti-trust suit about this in Europe recently... you may have heard about it?