Not really true: because as I pointed out SteamOS is more about the OS, not about one single machine having to be a sure fire sell system. Many computer's can already be a steam machine without having to buy new hardware. Or even if people would have to buy some new hardware they in effect would be able to download the SteamOS and do it for free for open hardware be that a Pc they already have, that's because it can be made to even run on small single board systems to boot.

Microsoft is moving in the right direction, its just that already SteamOS is already to that level, Microsoft waited too long to offset the increase presence by other OS's that will have an increased Adoption Rate over what Microsoft could have if they would have made a xboxOS for an entertainment OS for any hardware for any company's hardware which means less of a reason to choose other GamerOS over a Microsoft offering 

Simple like that: graphical capable PCs have just become affordable thanks to new GPUs. So Microsoft was forced to build their own console.

BUT: the next gen GPUs are just around and will run circles around a PS4 or XOne - while the complete systems will costs less then the consoles.

Expect Microsoft to release a free XBoxOS in the near future as Facebook will show up with their true next gen console for Oculus Rift utilizing the true next gen AMD x86 APU design.

I am not saying this from a Linux/Android point of View, I am saying this from a point of view Of consumer electronics in general and has far increased its own general computing platform in of itself. A massive growth area even more than PC's ,I  was saying this from an Adoption of the OS point of View. If you have not noticed other OS's that have been free for years are now getting main development support that to be blunt only really Microsoft has been able to gather for only a Windows OS only in the past but now its changed more in line for other OS's than even Microsoft in this growth market.

You said niche markets: but If you have not noticed Android is not a Niche, if anything Windows phone is the Niche market! 

Nothing wrong with being a Niche, but what I am pointing out is Things has changed when it comes to OS's that even though they are not Windows, Microsoft no longer has a lock on being the only real OS support for gaming on PC now. That is not to say in PC that Microsoft is still not the leader, what it is showing is now the main OS for consumer electronics are not a windows OS powering the box, its not a windows OS powering the TV is Linux and Android.

That is more than just a very niche market.

I do not think they were forced, they were pitched the idea, but if you look at now, do you think a XboxOS that could be loaded on every consumer electronic would not have been a better choice, of just releasing only.  A single box?

As for free xboxOS I do not think it would be free , I think it would be smart to do so, but I do not think Microsoft will make a xboxOS basic or Xbox pro OS for instance.

If they do it would be a way to at least keep another GameOS FROM MAKING more HEAD ROOM than they already have .

To be honest, Steam Machines will probably be the biggest flop of 2015, if they don't become a vaporware. It's a bad idea generated by pure despair from Valve that MS may plan to get on the Windows PC gaming scene and create problems for them.

MS is closing Windows, just like Android and iOS are closed environments: one store, one way to get apps/games and the owner gets its percentage.

Let's suppose that I have a Windows PC and a lot of games on my Steam library. Why would I replace it with Steam OS and lose compatibility with all my old titles and most of the new ones? CoD, Far Cry 4, Fifa were released some months ago and won't run on the Steam OS. Why would I do a change in my PC that would only make it worse?

'Let's suppose that I have a Windows PC and a lot of games on my Steam library. Why would I replace it with Steam OS and lose compatibility with all my old titles and most of the new ones?"

Let's put it another way, back in 2007, Steve baller stated who was going to replace a windows smartphone with a subsidised $500.00 smartphone with no keyboard!

Right now valve is developing for the steamOS,  dropping windows completely right now is out of the Question, but as time goes along who knows.

The newers smartphone is better than the older one. There isn't a subside that will avoid the fact that there aren't games for it. If you want a subsided machine that's cheap, buy a console: it runs way more games than Steam OS.