I imagine most developers could find a job with similar pay in a month or maybe one and a half, so the reasons would have to be strong enough that you'd give up an extra 10% in salary, or even being able to take a 3 month long vacation.
On the other hand, if they recently had to move to Vegas I wonder how hard it is to find work there and I can totally see people not wanting to move again so quickly.
Of course, those who have reservations about working where they are, should take the severance package, but that's the point.
Also, I am a bit surprised that we are discussing 3 months of pay as a magnanimous, almost foolish, concession from management, whereas in many places around the world that kind of compensation is law mandated when you lay-off people without reason.
Geographic area heavily influences this. Last time, I spent 8 weeks with almost no nibbles (and then suddenly had two companies fighting for me on the 9th week).
I've got mouths to feed. And when you interview for your new job, you are going to be asked why you took the buyout. "LOL 3 months salary" isn't a good answer.