I can see how they would be an advantage to some, but a detriment to others. I don't find any of these things to be enough of an advantage to outweigh the advantages of having it in browser.
> You don't use a task bar on your computer?
Nope.
> You would never want to be able to alt-tab to a programming IDE or music player?
Having these in browser means 1 less window to keep on the desktop taking up space so I don't need to alt-tab as much. I can see both my IDE and my browser at the same time.
> [ .. Atom, more interactive app section ...]
I don't use Atom or VSCode (electron-based editors) so this isn't an issue for me. But I can totally see wanting these to be as native as possible, so using them that way makes sense. So I'll 100% concede the point for code editors.
For data I use Firefox containers to keep that things compartmentalized sufficiently so there to no need to worry about polluting local data stores.
You don't use a task bar on your computer? You would never want to be able to alt-tab to a programming IDE or music player?
You can't imagine why someone would want to be have a programming IDE like Atom that didn't need to pop up a dialog box literally every time you wanted to save a file to disk?
You can't imagine why someone would want an IDE like Atom to automatically read from their local Git config and hook into native commands for functionality like file grepping? Or why someone would want to be able to use native volume controls to separately control volume in a music player and their overall browser?
You've never wanted to start a long-running process in an application and then alt-tab to a separate program while it completes without that process getting throttled?
You can't imagine why someone would want to clear all local data from normal websites in their browser without also clearing all of the local data stored in every web app that they're using? When you want to clear some old files on your computer or empty your trash, do you prefer to just `rm -rf` your home directory?