I carry a SPOT because I am solo most of the time, often in remote areas with no cell phone reception. Out here, a big worry is: bites by Mojave Green rattlesnakes. Plus, I often send my wife a "delayed" message if I anticipate needing more time. I have medical conditions (e.g. kidney stones) that may cause me to take more time, and I don't want to start S&R if it is just a matter of slowing down for painkillers. It puts my wife's mind at ease (relatively).
Chacun à son goût. I went solo for years without ever using SPOT or GPS. I still don't take a cell phone with me.