When I lived in the desert, the local newspaper regularly published stories about tourists getting lost/stuck/stranded and then dying.
Going by the newspaper accounts, I'd estimate at least a dozen people died in the desert each year, and that was just in my area.
And that's not even counting the lives saved.
Here in Las Vegas we have a ring of mountains around the city--and virtually no cell coverage beyond that ring. Even within the ring the outlying areas are often shadowed out.
I was unable to find nation wide stats on search and rescue events.
[1] https://www.adirondackexplorer.org/stories/record-number-of-...
I wouldn't be surprised if there's a lot of midwest areas that have a similar problem.
I have never not lost cell coverage when going on a hike in the mountains, and I only go on casual day hikes.