I have used Firefox for long periods of time, mainly because Google stores everything I do with Chrome. But Firefox is just too resource hungry. Slow at times. Even for development Firefox is a hog. At least it feels like it. So I end up using Chrome more.
There are many reasons, but when you trace it back, it all comes down to:
1. Google doesn't have to directly make money with Chrome. Which means they don't do anything that's against user's interest. Mozilla needs to make money with their browser somehow.
2. Google has much more money
3. Firefox is virtually non-existent on the mobile scene.
This manifests itself into all kinds of weird things Mozilla does that really don't make sense from user's point of view--they have to make money somehow, they have to grow their userbase, and all without spending much money.
For example, making Yahoo the homepage for me was a dealbreaker. I know you'll say you can just change it, but people are lazy. They just want everything to work out of the box, and time to time I use Firefox but it really leaves a bad taste in mouth whenever I open firefox just to be greeted with Yahoo search engine. And Yahoo does a lot of shady things on their side too, so it's pretty negative image.
Integrating the now-acquired Pocket into their bookmarks bar and shipping it as a default was a weird decision too. I'm guessing it was something like "we need to compete with google but we can't get into cloud business so let's just use these guys and see how it works out", but it was super weird.
Firefox first gained traction over IE because it was super lean. That's not the case anymore, at least in my view.
>Firefox is virtually non-existent on the mobile scene.
I agree with (or at least understand) most of your post, but I'm a bit surprised by this. Having used Chrome, Dolphin, and Opera on Android over the past few years, I have always come back to Firefox. It's speedy, has most of the extensions I want, and sites render nicely, though occasionally it hiccups on esoteric scripts and I end up loading them in Chrome (if I actually need to).