Let’s face it if you’re able to get the phone out of whereever you’ve stashed it and are in a good enough state to phone the emergency services with your location and needs then you’re probably not badly injured enough to need those services.
As people above have said, it depends. It might also not be you that needs the help.
One of my students got her foot stuck in a hole while walking alone last week, and there was no mobile signal. Fortunately, the farmer who found her had a phone and didn’t have to go far to call 999.
They had the saw out ready to remove her foot, but fortunately managed to free her in time. Had they arrived any later, because the farmer had to go all the way to a phonebox or house to call for help, she’d have lost her foot.