Look at Apple. Their users buy new stuff all the time. Their sales always surpass previous sales because the user base is willing to move with technology and use their money to do it.
I do understand your point. But the thing is Apple has very large network of service, plus lot of network providers sell it on contract, plus it has all the rich user base already and has become a status symbol. Also it still gives new OS to old devices no matter how they work. Do you believe any of the point is valid with MS at this point of time? No one at any store promotes windows phone even with W10. Hell no one knows what it does better and different than android. Second, why should anyone spend money on on so costly device with W10 (L950) when no one knows about it and is not a status symbol? Third, why should anyone spend anything on cheap device with W10 when no one knows what it does better and has limited choice for the device itself? Simply, costly = go iPhone, cheap = go android.
People with old device would have gone for new windows device happily if MS did not break the trust with false promise. Everyone is not unhappy because MS did not give W10. It's because now its clear that WP8.1 is never gona get features all were waiting for, apps will be the same. Its like MS is forcing to burn their pocket to buy new phone which no one likes. Android and apple do it but subtly. They do not put a such a show. They give new OS which after actually using in current device, user knows now its time to upgrade. Couse he knows what new OS can do on new hardware. Here we had W8.1 with lot of flaws, poor apps and now MS wants us to get new phone with out letting us know what good it can do. Whos gona spend money again just to see whats good in w10 when they have such great experience with wp8.1?
Users with old device are crutches, development for old hardware is a burden is alright from business point of view, i understand. But it should be when you have perfect grip over market. Till then you have hold on to everything you have. Anyway. I really wish whatever I feel becomes totlly wrong. But the time will tell.