Hikermor,

As I said it is very much terrain and situation dependent. I have only limited experience hiking in the desert SW, but many areas looked like they would be quite reasonable to send a SAR team into at night. And I have no doubt whatsoever that back in the day, SAR teams were much bolder and tougher than today. But some situations are more dangerous in the dark.

SAR leaders continually have to make difficult Risk vs. Reward decisions. Whether or not to send teams out into difficult terrain at night is one of them.

I can do no better than to quote from Tim Setnicka's dated but still classic book "Wilderness Search and Rescue". At the very end of the book, in the chapter "Final Thoughts", he tells the story of Jack Dorn, and a rescue in Yosemite.
Quote:
Three rescues developed almost simultaneously and all involved long walk-ups in foul, sleeting weather. Jack was part of a group sent to hike up to the Valley rim in the early morning hours by the Yosemite Falls trail, a freeway by local standards. When his party of six stopped in the sleet to take a break at one point, Jack was nowhere to be found. When it became light, the team found Jack's body at the base of some rock slabes 200 meters below the trail. For unknown reasons - probably a combination of wet moss, fogging glasses, and an instant of carelessness - Jack had slipped off the trail and slid down the slabes to his death.

The two climbers Dorn was walking up to rescue were safely pulled off the rock early in the morning. .......it appeared that they had sufficient gear with them to rescue themselves. All the noble idealism of SAR melted down to a puddle of nothing at all when measured against the situation in which Jack Dorn lost his life. It was a tragic waste.
_________________________
"Toto, I've a feeling we're not in Kansas any more."
-Dorothy, in The Wizard of Oz