But I fail to see why we can't have a full-featured browser front-end that uses Webkit, V8, etc as libraries. We have a lot of these projects, but they are always very spartan on feature-set, portability, extensibility, etc. It's almost always a team of 1-5 hobbyists, instead of a serious team of full-time employees. At $30m per 1% of the market, there's a whole lot of money to be made.
Just make it look like a native app on each major OS (Windows, OSX, Linux, BSD), let me move all the toolbar buttons around, let me put my tabs where I want them, let me load my ad blocker and script injector, don't spy on me, don't pack it full of adware, and I'm a happy camper.
The reason, to my mind, is simple: unless your underlying technology is better, there's little reason why users should choose your fork over the engine's official skin, which is always going to have better integration, will be first to get new features, gets security updates first, etc.
1) There aren't more competitors 2) A subgroup of them hasn't agreed to a conformant subset of HTML/Javascript/CSS and stuck to it
A browser is just the most complicated piece of software that there is.