Simpy put. If one allows themselves to get into a situation where they need to get the phone battery charged for any of the reasons you listed then they have failed to plan.

What good is a solar charger when a person(s) is incapacitated and is under dense tree cover, when is raining, snowing, overcast which can often last for days.

I am not saying you are wrong by thinking of the usefulness of the charger and it is always good to see technology that has a useful purpose, I just would not bet my life on a solar charger nor would I bet my life on a phone in general.

There are 2 sides of cell phones and lives saved, unfortunately one side does not have a good outcome and many of those people were ill equiped for the environment and terrain they were in to begin with.