The Yavin system is arguably well off the beaten path. You don't put your hidden rebel base inside an ancient pyramid if you're going to have tourists or locals mucking about. You also don't want any inhabited planets nearby with space traffic who could see your comings and goings, and make approaching hostiles harder to spot.

I got the impression from the ending of ESB, and the events in Jedi that the Rebel fleet has adopted a nomadic existence, not unlike the rag tag fleet in Battlestar Galactica.