Interesting - it really doesn’t make sense to me why UWP has been designed this way. I was looking forward to it as i didn’t really understand the technical aspects of the system. For me it was just an additional selling platform - and if it would be that way i believe i would support it - as a small company i would look forward to have an additional selling platform next to Steam. Don’t get me wrong on Steam, i love Valve and working with them, everything is so smooth and they are really there for you when you need them - but having an additional option to sell your game wouldn’t be too bad. Humble Store isn’t really an option, it has this ‘selling dead games’ flavour.
As for Unity, well i made my first game under Unity - no way it would go back, even with all the money spent on licenses and assets.