@Moon @jeremiah @mcread web kinda is the best thing we have, apart, say, macromedia flash and likes, which are dead.

When making a UI you'll most likely face 3 kinds of problems:
1) you need some custom component
2) you need to render a rich document (even just text with hyperlinks), possibly with formatting, i.e. chat messages, emails, etc.
3) your entire UI might as well be an Excel table or Access database that need to be accessed remotely or integrated into something else.

Custom components are incredible pain in the ass to make, imagine having to manually do canvas for something trivial. Meanwhile in web you have the versatile <div> that can do pretty much anything, there's barely anything like that in Delphi, Qt, WPF etc.

If you need to render something "rich" your only options really are either RTF component (very limited), embed a browser, or get some custom component that's bound to be proprietary and expensive and quickly outdated, so people stuck with browsers, email viewer is a browser, chat view in older messengers are often browser, and if you need to render multiple contents, it's more efficient to just use one browser for all instead of spawning separate browsers for each, especially for things like chat messages.

If your UI is a glorified excel table or database, it's much cheaper and convenient to make web ui than trying to make some sort of native application (or making remote MS Access forms or whatnot)

If you look at point 2, you can see how browser ends up overtaking the entire application as you need more and more from it.