Because they can't imagine for a moment that 3 years from now when they want to get the band back together to support Rand Paul for Prez in the GOP primaries, that they may encounter some members of the band who will insist upon, and/or perhaps actively pursue, a Ron Paul write-in campaign instead.
Does anyone know who holds the record for receiving the most write-in votes for President? I think if he's not the nominee Ron will likely break that number this year (if write-in's are even tallied). A stat that will punctuate the end of his career as a politician. "Ron Paul beats [record holders name] for President".