Essentially, all jQuery has done is drop support for Internet Explorer on Windows XP and Vista. Fully updated, XP runs IE8 and Vista runs IE9. Google Chrome did the same thing 2 months ago when it started requiring Windows 7 and up. Windows XP support was dropped a long time ago. Vista is still supported, but only used by a small chunk of users worldwide (about 1.4%). While XP still has a larger worldwide userbase (around 10%), most companies and individuals don't consider them worth supporting or advertising/marketing/selling to.
jQuery does still support both IE10 and IE11, so it's not like they're dropping all IE workarounds as stated in the title.