Many tech companies (thankfully) invest to various social responsibility programs so the question is - why not to give up the income from the IE8-IE10 users as a part of social responsibility program?In this case it would be educating users about safer browsing and improving the overall Internet security.
However, in the case of the old IE versions we need to look at that in context: In fact, it’s highly probable that nine recently fixed vulnerabilities in Internet Explorer also exist in IE7 and IE8, and in IE9 and IE10 on Windows editions ineligible for patching.
As Gregg Keizer states in the above article: The danger with known, but unpatched vulnerabilities is significant: Cyber criminals regularly parse updates and compare “before” and “after” code to determine what was changed.
Getting hacked can have serious consequences (especially in the business environment) which go far beyond the inconvenience of not being able to use the website with the old browsers.
If users cannot upgrade their browsers there is definitely someone there who is responsible for that and should get the message.
Windows Vista SP2 lifecycle ends on April 11, 2017, so it is still possible for more than a year, that some of your users will use a patched version of this browser.