1) We don't cater to IE9, which is at 5.11% according to stat counter. IE9 is a bad choice point for this - it's the first IE that had auto-update. Everyone left. We're catering to IE8+; 8 is currently at 6.5%.
2) You don't count the version; you count the version and all its successors. That is, we're not catering to 8, we're catering to 8+. 8+ is at almost 35% and is still the dominant aggregate browser.
3) Where does 14% come from? This says 6.8%, or roughly half what's claimed, in the same neighborhood as the browsers mentioned: http://www.practicalecommerce.com/articles/1417-Accessibilit....
4) You can't cater to disabled users. They're not one thing. What you do for the colorblind isn't the same as what you do for the blind, which isn't the same as what you do for people who have specialty control systems, which isn't the same as what you do for micro-screens, which isn't the same as what you do for people who have motor control circumstances, et cetera.
5) The web solution for this is WAI-Aria, which began in mid-2012, and became a candidate recommendation three months ago.
6) Microsoft has been requiring WAI-Aria for store apps since late 2012.
7) Most people have never heard of WAI-Aria.
8) As far as I know, no single group of disabled users reaches 1% of the userbase.
9) Supporting old browsers is way, way easier than supporting disabled users. Old browsers mean installing a shim and fighting a couple bugs, and that level of effort leaves people writing angry blog posts for five years. Supporting disabled users means learning how (there's basically no tutorials, but ample angry blog posts with bad statistics) then finding someone who has the equipment to test it on, then learning that you have to re-order everything on the entire site because the reader software can't be told that the source order isn't the reading order, then adding several properties to every single tag on every single page, then having no way to audit.
10) Many of us /do/ cater to the disabled. Your site has no aria markup at all, is peppered with empty iframes (which will wreak havoc on older readers,) and is covered in images that have no reader equivalents. You are actually substantially less disability friendly than the average webpage.
11) Even people with full sight find a font and color scheme like that very difficult to read.
12) In short, because like you, most small web authors are more comfortable writing about the problem than being part of the solution.