It seems to me there are two benefits of the Windows Store:

- Discoverability.  You may not know a lot of people who use the app store, but you're probably coming from a biased perspective of an experienced computer developer. For less tech-savvy users, this is one way they discover new programs.

- Trust. Many users have rightly been warned against downloading and running arbitrary executables from the Internet. I think the Trust factor of Inkscape's official download pages is pretty good (certainly a step up from SourceForge with all its pop-up ads), but again: for new computer users, the Windows store is a strong marker that this is a real, safe program.  (Which Microsoft enforces with signing requirements and sandboxing limitations.)

I would urge everyone not to get overly caught up in the "app" terminology.  An app is just an application, a program, some software, renamed thanks to Apple's massive advertising campaign of the last decade.  Yes, many modern apps also share other features (like relying on internet services), or a certain mobile-focused look & feel, but that isn't essential, and isn't what is being proposed here.  

One way to think of the Windows Desktop Bridge seems to simply be a new installer package, one that plays well with the Windows store and modern notifications and update methods on Windows.  Functionally, the main change is that the software is sandboxed when running, so that all file system access goes through the app wrapper.

Docs for Windows Desktop Bridge are here: https://docs.microsoft.com/en-us/windows/uwp/porting/desktop-to-uwp-root

My remaining questions would be:

- In addition to the development time required to initially set up the Windows Desktop Bridge (Which David at Microsoft has offered to help with), how much additional maintenance work will be created by having a second Windows installer package?  How much administrative complexity will be created by working with the Windows store?

- Will Inkscape scripts & extensions still work with a sandboxed application?  What about command line features?  If some features won't be available, how will this be communicated to users? Could there be some way to let someone upgrade to "developer mode"?

- Does the Windows store provide an environment for successfully communicating the key features of the project, linking to additional resources, and requesting donations?  Alternatively, as Martin suggested, could some of this information be more effectively integrated into the app itself (such as a splash screen on load)?

(I agree with Marc that putting an obligatory price on app store downloads would effectively be penalizing new or less-savvy users.  If it is possible to add an optional donation to the download page, that would be great, but it shouldn't be free if downloaded from one site and paid from another.)