On the other hand, Mozilla has done a lot of stuff which is outside the scope of "Firefox", but which is good for the community as a whole. I mean, that's what Firefox was originally: an offshoot of the Mozilla monstrosity that Mozilla (the organization) took and ran with, to everyone's appreciation.
Plus, if people were donating towards Firefox specifically, how many of them would be upset that Mozilla was spending "their" money on developing a whole new programming language? "This is a waste of my money, just use C++ or something instead of reinventing the wheel".