In Apple's defense, the SOCs on iPads are improving much, much faster than PC chips. Intel chips have been getting faster at something like 5% per year for the last decade, compared to 50% for Apple's A-series. So I think supporting 5 years worth of iPad devices is somewhat comparable to supporting 20 years worth of PC hardware: in both cases it's about a 100x performance difference between the bottom and top, and beyond that I imagine it's not worth it to try and tune an OS for both.
That really isn't a like-like comparison. You are looking at just one product from Apple. In the Android and Windows world for each generation there are hundreds of thousands of hardware combinations from entry level to high end that are expected to run Windows. Also MS/Google cannot test their software with future un-released hardware. If anything, this should be a cakewalk for Apple - if they choose to. I don't know what special "tuning" is required that prevents Apple from supporting the hardware.
If that is indeed the real reason, its unfortunate that they cannot get an OS to run acceptably in 1GB of RAM. Especially when they have such a tiny amount of hardware variations to support.
Microsoft and Google both release their own hardware. AFAIK, Microsoft does a pretty fair job updating software for the Surface. The same cannot be said for Google and Pixel (Or for that matter, Nexus prior to Pixel).
Microsoft supported Windows XP for 12 years, Windows 7 for 10 years (+4 years if you are willing to pay for extended support). During the lifespan of XP the Moore's law was very much working.
The big difference here is Windows XP and Windows 7 had nearly static feature-sets over their lifetimes (or in the case of XP, SP 3 quickly became the baseline). For the vast majority, Windows XP that shipped with your computer was the same for the lifetime of that product. iOS changes features every year, often quite significantly. The challenge is whether the next version of Windows supported your hardware and this was often not the case. If your OEM had funky components and didn't want to update the drivers to the new version of Windows you were SOL. Windows has changes a LOT since XP/ Windows 7 and their update model is more like iOS than XP now so it's hard to use the old model as a baseline.
The OP said that Apple doesn't have to support older devices because they are antiquated as far as performance goes. So I gave an example where software was supported for far longer during bigger increases in performance.
You are saying that as long as the OEM updates drivers for components support is possible. I agree. This is a reason why Android is often not updated even in the modding community (Qualcomm is not releasing drivers). If only Apple was responsible for both the software and hardware... Oh wait...
