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.