I get your gripe, but there's a good use case for this stuff in building dynamic web applications. Just because a technology is misused doesn't mean the technology is to blame.
Browsers aren't general purpose applications. They can't fill every application role on the computer. The more "web dev" tries to push them in that direction, the slower, more difficult to develop and maintain, and generally poor they will be, and then the "dynamic web applications" that run on them will suffer.
What, for instance? Your comments seem heavy on condemnation but light on substance. Sure there are certain donation specific tools such as Photoshop or 3dsmax or ableton etc that wouldn't work in the browser, but for your day to day business 99% application, the user generally does not need to do anything that the browser cannot.
The fact is, the web world is evolving at an extremely fast rate, and leaving the native world in the dust.
I don't argue that the browser cannot be made to do something. I merely point out that making it do "everything" will only end up in disaster for browser creators and maintainers, and for app developers alike.
The "web world" hasn't even caught up to the native world yet. It may be evolving very rapidly, faster than native, even, but it's still behind.