AppVeyor: update to Visual Studio 2017 #3606
It's probably worth leaving in the last version that can target Windows X, where X is XP/Vista/7/8 or whatever it is that we still claim to support. Presumably, people who are still targeting older versions will be using the latest SDK that still supports it.
Anecdotal. I just haven't seen it that much. I would also like to reduce the number of builds. I did some empirical searching
Visual Studio 2005 - 182,259
How about 2008, 2010, 2017, and we will eventually need to add support for 2019 due out this year.