And your point being?
Nothing stops developers from selling anything they make for Windows Store in other Stores.
When it comes to smartphones, it's no different from say Apple's store for iOS.
When it comes to tablets, what do you know it's just like regular PCs. Developers can sell anything they make for the Windows Store in any other store they want.
UWP's main benefit is being able to run on Consoles (already locked to Microsoft) and smartphones (already locked to Microsoft). On PC it's business as usual. A developer can release UWP in the Windows Store so it has access to smartphones and potentially consoles. On PC they STILL can release on whatever store they wish.
Yes, some UWP programs aren't sold in say Steam because Steam wouldn't want to sell most of that stuff anyway.
My god the paranoia of some people out there.
So for the thick headed.
You can't buy Apps for Smartphones except through the OS holder's storefront (without jailbreaking).
You can't buy Apps for Consoles except through the OS holder's storefront.
UWP is no different from Apple or Google in that respect.
On PC, NOTHING changes. A developer that offers a UWP app in the Windows Store is free to offer the same app in Steam (if they'll accept it) or Origin (if they'll accept it) or Gog (if they'll accept it), etc. It'll run fine on PC's (tablets included unlike Android or iOS) just like the Windows Store version. But if you want to run on a Smartphone or a Console, you'll have to go through the platform holder...just like every other company on the planet.
People don't have a problem with Apple or Google or Sony running things this way, but they get their panties in a twist if Microsoft does the same thing for apps that can run on Smartphones or Consoles? Yeah, I can taste the hypocrisy from here.
BTW - you can technically buy UWP apps through Best Buy, Amazon, etc. Just buy a Microsoft gift card. It has the same exact effect as buying a Steam Game through Amazon, as you still have to redeem it through Steam.
Regards,
SB