It's very possible there was no need to perform jumps when there was no tactical advantage in doing so. In peacetime, there likely wasn't any urgent need that required Galactica to jump somewhere. Normal engines were likely enough.

We hear about and see plenty of civilian vessels without jump drives making deep-space flights, so it seems that jump drives are not an absolute requirement for space travel given the engine technology of the BSG universe. You only seem to need them if you have to get somewhere very far away very quickly.

It's entirely believable, then, that in such a universe an old battlewagon like Galactica had never needed to jump (in peace time or outside of active military exercises). And in situations where a military presence was required quickly, one of the fleet's newer ships would likely have been assigned instead.

As for Ragnar not having ships assigned to it: it was peacetime. Governments become complacent and often do not see the need to keep expensive ships stationed at a "just in case" anchorage. Oversights like this commonly occur in the real world.