For paperhero: Can't say for sure. Probably has to do with whether Windows 10 runs the required version of DirectX significantly more efficiently than Windows 8.1.

For wizard_of_woz: Sort of reminds me of the 8th Medical Battalion in 1977 where perhaps 10 percent of the deuce-and-a-half drivers were born before their vehicles were manufactured. None of us was alive when the truck was designed. But it did what we needed and the Army had better things to do with the money required to acquire and field a newer, more capabler vehicle.

P.S. I wouldn't mind driving that old beast on the freeway today. So you wanna play chicken? I got more steel in my front bumper than you got in your whole SUV.