There is more to leaving one coaching job for another than just which program is more prestigious or which one pays the most.
Many of these coaches are not just vagabond gypsies looking for the next place to stop for the night. You're talking about a major relocation (sometimes to another part of the country) that can involve uprooting small children or even elderly parents. You're also talking about uprooting a coaching staff and support staff, not to mention the separation from players you've recruiting and may be very close to.
For every turncoat like Fran and his ilk, there are coaches out there that remain very loyal to the people they work for, the people that support them, and the program they've built.
While I think it's often disingenuous the way some coaches use job openings to leverage a new contract or play one school off another, I can understand why--at the end of the day--they decide to stay put and not undertake a major move, regardless of how prestigious the suitor may be.