Home users generally don't pay for Windows. It comes with their computers and the major version upgrades are free and have been for quite some time; 7→8 (2012) was the last time it wasn't free but 7→10 (2015) was a valid, free upgrade path so most just bypassed 8 entirely (and they were better off for it because 8 sucked). Since Windows 7 was itself released in 2009, most home users haven't paid for Windows upgrades in 16 years.
Yes, having to maintain an OS over multiple years without recurring revenue might be an issue indeed. On my side I wouldn't mind paying a subscription if the OS could respect my choices. But I guess it does not really make sense to provide a subscription that only a very small handful of people would pay.
(I wonder how subscriptions could handle multiple machines; today it often happens that people have multiple computers but subscription cost would quickly add up; I guess they could have different tiers with different allowed concurrent use count)
