I think it's worth linking the 12.4.9 page because it's impressive that the software update is available going all the way back to the iPhone 5s. That's some serious longevity.
Well, yes, its better than your average Android vendor. But on the other hand Windows 8 was released 2012 (i.e. about a year before iPhone 5s), and is scheduled to get updates until 2023. That is pretty serious longevity. And supporting handful of Apple devices must be comparatively simpler than supporting the hodgepodge fleet of Windows 8 devices.
8.0 which was released in 2012 is no longer supported, with the last updates landing in early 2016. [1]
8.1 on the other hand _is_ supported until 2023. [2]
The majority of 8.0 users immediately upgraded to 8.1 (because 8.0 was slightly terrible), so you're mostly correct. 10 years of support is pretty standard for Windows releases.
Apples (ha!) to Oranges. Personal computers cost, on average 2-4 times what the 5S cost in its day, and are expected to last much longer than a phone (as evidenced by the lack of uproar that all phone vendors including Microsoft drop support within 2-3 years ... except Apple).
Well, yes, its better than your average Android vendor. But on the other hand Windows 8 was released 2012 (i.e. about a year before iPhone 5s), and is scheduled to get updates until 2023. That is pretty serious longevity. And supporting handful of Apple devices must be comparatively simpler than supporting the hodgepodge fleet of Windows 8 devices.