They are making money off the store, I read an article recently that they saw a massive increase in revenue YOY just from December alone.
I will say, your post does come as somewhat contradictory as you are arguing that this is here to say while in the same breath mentioning how many times they have made sweeping changes to strategy.
Contradictory, no. I put that into perspective that I understand why people are hesitant to use such a service but also realize the realities of them doing so to businesses and customers. Let's say the Windows Store does get 'large' and then they abandon it, the backlash is much larger than "just" gamers. It's businesses, it's regular consumers of their surface, surface pro, surface hub, surfacebook, Microsoft band, lumia phones, 3rd party computers, 3rd party tablets, 3rd party phones, xbox(gaming), hololens, office, etc... All the things end points in which they get money would be affected, IF it got large (which they want it to be). It's like if Apple abandoned the App Store now for something else. Yea, those other things will still work but how many people would trust it.
That's all I'm saying. Windows Store is basically their next Win32 paradigm but in every device running Windows.