When the GPL was written, this kind of software wasn't very common. Now that it is, the FSP formalized the AGPL, which they recommend over the GPL for server-side software.
Nearly any software is potentially server side software. So really they should recommend AGPL for everything, and relicence all FSF owned projects as AGPL.
They don't because a lot of people even inside the FOSS community are violently opposed to the AGPL. Quite a few people think that it conflicts with Freedom Zero.
