You make an excellent point. Rescue can be hours, even days away, even in the best of circumstances. Helicopters can be grounded due to pilot fatigue, weather, maintenance, other missions, you name it.

Another point. Some wilderness accidents result in immediate consequences for the victim. If you fall 50 feet onto solid ground, activating the PLB will only result in speedy recovery of your remains. Drowning also occurs quickly and typically rescues depend upon those immediately at hand. Falls and drowning are the two main causes of back country fatalities. Only prudence and self awareness can truly keep you safe.

SAR will do everything possible. I have responded at every hour of the day or night, sometimes walking into building winter storms, or headlong into the searing heat of a desert summer day. But SAR can only do so much.