Well, keeping an old machine or VM around to run an older version of Flash is much less of a burden than using one to run Flash Player. It's normal to have old equipment if you're a professional, and if not then creation tools don't have as many significant security issues so you don't have to rebuild the VM as much.
It might still be more work than people want to put up with.
...as long as you have the original Macromedia animation software up and running, I presume?
I've seen a couple of good Flash players. Is there comparable open (or even closed but maintained) Flash animation software?