This works until one of that "stable selection of apps" tells the user that the version of their OS is not supported anymore, and that they would have to update

This works until one of that "stable selection of apps" tells the user that the version of their OS is not supported anymore, and that they would have to update. If the device is locked, your update paths are limited. Just because not everyone uses all functionality doesn't mean I have to condone removing that functionality entirely. And it does not mean that it might not burn a user at some point in the future. As an anecdote: we have an iPhone 3G in our household, a phone that became progressively worse with certain updates after the release of both the 3GS and 4, to the point that it is nearly unusable for surfing now. This leaves me with exactly two options: stop using it as it was meant to be used, or buy a new phone. And for the other camp: in order to get an inofficial version of Android that is newer than Gingerbread on my phone, I would have to reformat its internal storage, which I can only do since it is unlocked by now. However, even that is not entirely without risk, and it is not supported.