I think this drastically underestimates or at least undersells the impact of convenience, or in this case the maximum possible level of convenience which is already having the feature even if you don't know it. Similar arguments could have and indeed were made for every other small electronic device the smartphone has replaced. It's not that the advantages you listed don't exist, it's just that they won't hold a candle to the explosion of smartphones with satellite messaging built in by default. I feel like even just 1 year (and 200 million satellite-enabled iPhones) from today pointing out these advantages is going to look like people pointing out that land lines have better audio quality and lower latency than cell phones.

I always carry my InReach with periodic location sharing enabled when I'm on backpacking trips. I also almost always carry it during international travel and road trips, but not usually with periodic location sharing. If iPhones start offering plans with periodic location sharing, I'm fairly confident that I'd stop carrying the InReach unless I was on a particularly remote trip that was outside of my comfort zone (which isn't something I really do anyway).