It is not uncommon for stations that run news and talk programming on FM to switch to mono during these shows. Other than the brief musical interludes, there's really nothing to be gained by running stereo. Mono improves the signal at the fringes and reduces multipath (always a problem in rugged terrain). Programs such as Morning Edition and All Things Cnsidered air during drive time, so less multipath is good when most of the audience is in the car.