I'd say they prove their purity because that's what distinguishes them from the rest. Now, if you talk in terms of projects successfully backed/run by the FSF,

I'd say they prove their purity because that's what distinguishes them from the rest. Now, if you talk in terms of projects successfully backed/run by the FSF, you may be right, there are not as popular as they were. But as guardians of the GPL ethos/politics, I'd say they do a good job (considering that this ethos hardly translates to money)