Perhaps it is these same NPCs that are commissioning the PCs to rid the town of the undead...in the real world, the leaders always have someone do it for them even if they are qualified - the generals are not going door-to-door in Baghdad.
Or, there is always the vacation/lord's conference excuse.
The famous NPC has stepped away for a time, thinking it safer to act, the baddies descend upon the area...
