But it's perfectly normal to depend on some OS parts and have minimum version requirements. Happens with everything out there, just that thresholds are different. Any recent Chrome doesn't run on Windows XP. IE11 doesn't run on Vista. Edge doesn't run on 7. Safari 7 doesn't run on OS X 10.8.
What do you propose to MS - to spend time supporting Windows Vista? Or make a browser that supports it? Bet they just don't care about Vista, besides security patches and alike stuff that they have to do under various enterprise contracts. Given that they go lengths to persuade 7 & 8.x users into upgrading to 10, doubt they care much about those versions, too.
I'm regularly in an office that is rife with XP. I won't be in that office to check the exact versions on all the installed Chromes for a couple of weeks, but they certainly seem up-to-date.