As to Why I want this feature and reasons behind it, there are a couple:
I want to install YouTube website as an app, make it to be on top of all windows so it won't be behind the program that I use. for example I want to code in Visual Studio and watch a YouTube video to learn something and apply it directly.
I want to have Bing or Google search installed as an app in Edge, launch the app, resize the window to have a rectangle shape, put it on the left side to have a side bar which always stays on top. now I can always quickly search for anything I want in that Edge app, no matter what program I use, because it stays on top.***
there are lots of other examples, where websites host a specific service and when we add it in Edge as an app, we will be able to use it just like a real Windows app and have it accessible on all programs if we pin it to be always on top.
***You could say that I could use Windows 10 search on the taskbar but It's not the same. because when you click on something, a picture, video etc, that is a link, the search app in Windows 10 will open it in a full browser window. what i would want is to view that image, watch that YouTube video, right from my Windows 10 taskbar, without going to a full browser window.
@HotCakeX Thanks for the suggestion. On first consideration, and in full transparency, this might not be feasible with some OSs. (One of our dev colleagues wrote a related piece on this a few years ago.) That being said, I'll still pass this along to our Web Apps team, in case they have a different perspective. :)
Fawkes (they/them) Project & Community Manager - Microsoft Edge