Different scenario with Machida.
Machida feels entitled to a full training camp because he earned a title shot. The repercussions of losing also played a big role in his decision not to take the fight on short notice. If he loses one more time to Jones he wont be getting a title shot for a long time.
Title shot entitlement + last title shot he'll get for a long time = reasonable not to take fight on short notice with champion
Machida did not earn a title shot. The UFC needed a way to make the last UFC on Fox card relevant so they promised him on but those same promises have been broken more times than I can count so his "earned title shot" is not worth jack ****. Machida may never get another chance to fight for the title and that is not outside the realm of possibility.
Jones is fighting Vitor, he could easily be booked against Hendo with a win and you know after Chael run through Forrest and runs his mouth he will jump to the front of the line. So we could easily be in mid 2013 by then and guys like Gusto and Glover are on the rise. Machida could easily be forced to fight and lose before he ever gets near another title shot. Especially when you consider that he was already not the UFC's favorite guy after the whole "Anderson Silva Money" thing and you have the fact that the champ already beat him and nobody is lining up to see or buy the rematch. Its easy to imagine a scenario where Machida just threw away his last chance at regaining the LHW title.