That's a good point about open source software not always being supported. I guess it's no coincidence that the large organizations where I've worked were all .NET shops, but all the Linux boxes ran Red Hat Enterprise. And the biggest complaint I've heard about about Microsoft not supporting old products was a discussion about Windows Server 2003 (In 2016...).
I don't think that "all companies are in on it" necessarily, but there's a reason for that kind of loyalty to customers and it's not because it feels good. I'm not going to knock Microsoft too much because while I do feel like they're off the mark in some areas, they're improving their developer support a lot recently so I'm excited to follow what happens. But I don't think it's a coincidence that they're rapidly increasing developer support either (we sat through the app-less wonder of Windows Mobile for quite a while). They are also of course a publicly-traded company, at the mercy of profit-demanding shareholders.
I would like to see a world where the people who use the products have an equal opportunity to contribute and improve it. Not someone behind a wall squeezing money out of pockets, or throwing candy at developers so they'll make their platform more appealing for them. Or at least as appealing as the other guys', else they go under. I'm hanging onto an ideology, I know.
Like digitalsushi said, this .NET job will let me retire but it still sucks. It could suck a lot worse though.