Having had some experience with 'people vanishing from public lands in the west," color me skeptical with respect to these junk statistics. Not all search efforts have a happy ending. This isn't the movies, but real life.
It is certainly true that expertise in SAR varies across the country, being the domain of the local sheriff, but I sense that the capability is commensurate with the demand and need for SAR. In Pima County, AZ, where I obtained most of my experience, SAR developed over the years (after an egregious fiasco) that integrated rather well with the local USFS and NPS jurisdictions. It has only gotten better in the years since I left the scene.
It can be surprisingly difficult to find an individual in the wild - a human bod, especially if unresponsive, is very small. A searcher must concentrate and be alert for clues,all senses activated. And there is always the possibility of intentional disappearance or foul play, as in the case of Paul Fugate, a uniformed NPS employee who was last seen leaving the visitor center at Chiricahua National Monument to check the nature trail. he hasn't been seen positively since, despite intensive and extensive searches. My assessment is that he met with foul play at the hands of drug dealers or similar, and was taken away and disposed of very discreetly.
I could go on, but enough......
Geezer in Chief