I carry a EPLB with a GPS function - but only when I am scuba diving from a boat in areas with strong oceaninc currents. If there are no strong currents then I do not carry the beacon.
The chance of getting swept away from the boat is not high, but the chance is present. At least on dry land you can call someone on a satellite phone and tell them where you are; but out a sea, when you are drifting with the currents,you need a beacon with a GPS locator function.
I've been carrying a SPOT for a couple years now. I like it because I can let my family know that I'm OK and they can see where I'm at on Goggle Earth or whatever they're using now. It has taken on more importance since I retired and do a fair amount of solo travel. Haven't had to push the SOS button yet and hope I never do, but it's some comfort to know it's there.