If you're the developer that's your job to tell that to your boss. Come up with analytics to support your findings, make your case, he's probably not going to be reading this thread and staying up to date on all the latest and greatest that's your job. He may be stubborn or you might find out that your user base is all IE6 I don't know but sitting around complaining isn't going to get you anywhere either :)
Analytics are irrelevant when you're writing some huge internal service for a company whose conservative upgrade policy dictates that only one older browser will be installed and used company-wide until God-knows-when.
By the way, glancing at a few browser market share websites, it looks like IE8 and IE9 are alive and well, totaling around the same as IE11.
Lol I am hardly "sitting around and complaining." At my last agency gig we had to support down to IE6 for several months until we built a strong case to only support down to IE8. Even still it was much harder and protracted battle than it should have been.
My fancy looking website doesn't have to look good on somebody's office computer. If they had a good firewall, it would probably be blocked anyway. Also, people still on old IE are used to seeing websites all busted up.