That's not really being fair; Windows was created decades before Android (one decade if you only count NT). The security model is different, because it was created in a different computing era.
I think the difference in API stability is a result of the different financial motivations between Microsoft and Google. For Microsoft, the OS itself was the product; to not make the APIs backward-compatible would have meant significantly less revenue and market share.
For Google, the OS is not the product. Google doesn't make any less money when someone continues to run an old version of Android. There is no monetary incentive to make new versions of the OS API-compatible with older versions, nor is there any monetary incentive to make new versions of the OS run on old devices.
Consider also that the cost of upgrading to a new (non-flagship) device in 2019 is much cheaper than in 1995. A typical PC circa 1995 could cost $2000 or more (price adjusted for inflation). Today, you can get an entry-level mobile phone for 1/10 that price. Back then, a family might hold on to a computer for five or ten years, because it was so expensive to upgrade. That makes paying $100 or so for an OS upgrade every few years worthwhile, because it's much cheaper than buying a new PC.
