Hello Elis-cal,
That's a really good question. If the Apple Watch SOS didn't work as expected, we'd verify the following related information:
- Watch app > Emergency SOS > Fall Detection is enabled and set to Always On.
- Watch app > Health > Health Details: Height, weight, and age are correct.
- Watch app > Passcode > Wrist Detection is enabled and working as expected.
- Watch app > General > Wrist Orientation is set to the correct wrist.
- Make sure the Apple Watch is on top of your wrist and snug.
At any time, you can manually enable SOS using steps found in: Use Emergency SOS on your Apple Watch - Apple Support
In case you still are unable to get SOS to work properly, then it would be best to contact Apple Support
They'll need to take it from here.
Wishing you well, take care.