It's plenty useful in some scenarios, like getting lost on a hike - it would significantly narrow down the search area for S&R.
This may be a thing that is specific to local conditions, though. It so happens that I live in upper Snoqualmie River valley, which has trailheads for many of the best and most popular hiking trails in the area. So, naturally, this is where most of my hikes are. And the towers that provide signal for the towns in the valley are on the surrounding mountaintops, so they provide coverage for a good chunk of wilderness around, as well.