(The statistics above are extracted from W3Schools' log-files, but we are also monitoring other sources around the Internet to assure the quality of these figures)
Their audience is predominantly tech savvy designers and webmasters, etc. It's not an accurate representation of the browser market. Even now, IE still has between 85 and 95 percent of the general browser market depending on where you go. You'll only see numbers like 50, 60 or 70 percent at places like wired or slashdot, etc.
But even so, yo'ud have to be a fool not to optimise your website to work in all browsers, in my opinion.