Exactly--which means Maxthon requires you to use a browser that they have defined. Firefox is a bare-bones browser. The user adds the functionality they want--no more and no less.
Yes, but that's essentially most of the "extra" features that are so highly desireable, which saves the hassle of downloading, installing and configuring the extensions like you have to do in Firefox. Is it small wonder why Maxthon won a whole bunch of awards lately and is actually used by Microsoft engineers, according to PC World magazine?