Re: it's not just about you
"Why did you arbitrarily exclude rooting and installing a 7.1.2 custom ROM? You are of El Reg's readership."
I'll include another reason. I can't install these things unless I've already gotten one of the android-makers' flagships. For these custom ROMs, the list of supported devices is rather short. All the expensive devices are there, but the nice thing that android has that apple doesn't is the availability of devices that have internals commensurate with their price. None of these get the ROMs created for them, and I do not intend to try to compile it myself. So my android devices rarely support anything other than the thing they came with. The devices that do get this are the flagships that are overpriced and underpowered. So my choices are too expensive but well supported (apple), too expensive with some rooting required and later no support because they'll use rooting as an excuse to say no (flagships), or sensibly priced but no software or support.
Another relevant problem is that these ROMs don't always offer all their functionality. They are buggy and require more user maintenance. I am capable of doing that, but I'd rather not do it for my friends and family or the devices I manage for my employer because a lot of stuff can break. This isn't like Linux on the desktop, where when something breaks it is easy to figure out what it is and slap in a fix, because things on custom android versions change a lot and a lot of things that break frequently are device-specific.