There are some really retrograde government and bigcorps, running ten year old infrastructure. And if that is your customer-base? You do it. Plus I worked on a consumer launch site for something you might remember, and we got the late requirement for IE7 support, because that's what the executives in Japan had. No customers cared, but yeah it worked in IE7.

Some corporate machines still run XP. Why upgrade what works?

I think anything still using ActiveX like stuff or "native" things. Sure, it should all be dead and gone, but some might not be and there is no path forward with any of that AFAIK.

Surely by this point someone has written a 0-day for MSIE 11 which gets root and silently installs an Internet Explorer skinned Chromium. If not, someone should get onto that. —Signed, everyone