I don't know if that's entirely true.

I do a lot of Firefox extension development. Many companies or users have a need for highly specialized functionality built into a browser, and Firefox provides an very rich platform for that. You can easily build powerful applications that integrate tightly with Firefox.

Chrome's extension capability is much lighter and more restricted; Chrome extensions are just light little packets of functionality that add to the browser. There's many things that you can't do that you could do in Firefox.

I think that area is definitely where Firefox wins, and will probably continue winning in the future.

Does everyone need that, and is it enough to keep a large market share? I don't know...but it is something that Firefox does better.