If the UX and latency requirements can be met with a web app, it doesn't support WPF/.NET maintenance/enhancement.
Web apps can do density so long as the latency requirements aren't too tight. There's where the banking folks spend their IT money.
they're generic applications, and their development
doesn't justify Microsoft investing in an entire stack.
I mean, I'm sure if you look at the statistics only 0.1% of users use Photoshop, or Premiere Pro, or AutoCAD, or SolidWorks, or Altium, or Matlab, or whatever - but if you drop support for all of them, what are users going to do?
Specifically, when WPF was launched all they could talk about were the cool 3D possibilities for doctors, researchers, and such... The reality has been less "Minority Report" than we had hoped, but those kinds of demands are growing, and very often will require the level of control over hardware that demands a desktop app.
In theory a lot of this is solvable with webapps, in practice there is a reason desktop computing environments exist :)
What about store managers restocking product?
What about developers working on complicated projects?
What about data scientists staring at spreadsheets?
What about power users?
What about anyone with the kind of intelligence that doesn't shy away from large amounts of information?
Do most designers ever think about ANY of these people? Modern app design doesn't even TRY to throw any of these types a bone. No "Advanced >" menus anymore, no pages of options anymore, nothing. It's all just 'sit down, shut up, push the button like a good stupid little user so we can all get paid.'