I think that it is mostly a matter of preferences.
There are people who change up to three phones in 3 y, spending more than 2000 €, just because they are eager for the "last-second" innovations. They probably can't wait to see the impact of, say, 4G, windows hello beta, edge-curved screens on their lives. Maybe, they give priority to saving a handful of download seconds a day rather than to saving their money. By the way, I doubt that a so far immature lumia 950 has allowed to save that much time, until AU update at least. I mean, it is fine, a respectable preference that supports the innovations.
Then, there are people who do not understand the importance of the updates, they do not care, until they have to face the problems caused by their old HW/SW. That is surely not the case in this forum
Finally, there are people, like many on this thread, who just prefer to seek a compromise. Not too old devices, but not high expense as well. With something more than 200 €, next year I will have had a 4y up-to-date Windows phone experience, with good performances (even rising recently) and only 2-3 minor issues. Not that bad perhaps, it was my preference anyway.
With respect to Samsung, I honestly think that they do not give the best support and the promptest updates in the world. We "suffered" a bit during the due 8.1 update but then they did forgive. For the current bugs, I believe it is a handful of code lines to correct in the firmware, but they will not do it because they simply are not interested. They are not Microsoft, that is increasingly moving against hardware generation barriers: a unified experience across devices. Even the Xbox One platform will evolve without requiring you to change your hardware!
In my opinion in the future the technology should struggle more against the contradictions of current hardware wastes. For now, I will survive some more time without Hey Cortana, Miracast etc. A Surface helps me overcome those shortcomings after all