United flight from SEA to ORD slides off runway at ORD
 

Runway overrun.
 

Do the CVR, FDR get pulled on an incident such as this?

With no aircraft damage or injuries, not an "accident." So not automatically.

If something in the initial interviews suggests there was a procedural problem (poor runway maintenance/plowing, poor ATC report of braking action, landed hot or long) or a mechanical failure (decel devices failed to deploy, nose-wheel steering, e.g.) - then maybe.

If, as some reports suggest, they had slowed to taxi speed but just skidded trying to make the turnoff - the FDR speed readout may be so low-resolution as to not offer much.

When you consider the extended procedure that applies when a CVR and DFR are recovered from a downed aircraft, is it fair use of resources in this instance?

I mean, it's not like lifting a cassette out of a tape-player and slotting it into a domestic player.

Yes and FDAP information will be derived from it to create animation. The pervious crew who landed prior to him will also be interviewed by the NTSB and FAA. Any time there is a departure from a runway surface, there is an investigation by all parties including union, airline and all government authorizes.