A bit of a follow-up to #507.

There are some feasible reasons why the Empire wouldn't just blow up Yavin to get to the Rebels faster, namely:

1. The Death Star's superlaser might take a long time to recharge for another shot.
2. The debris of Yavin might make it hard to target or shoot the moon with the Rebel base.
3. Yavin may have something the Empire would like not to destroy.
4. Probably the best one: Yavin is a gas giant, not a relatively small terrestrial planet like Alderaan was. Gas giants would take a heck of a lot more energy to blow up than a terrestrial type planet (which leads to other problems, see #153 and #160). So the Death Star might simply not be powerful enough to do it.