> I’ve gone camping and hiking in plenty of places that have no cellular service so cash is the only way to pay the fees.

This seems like more of a reason to push for rolling out wireless connectivity in places of natural beauty than to argue for keeping cash around. Last time I traveled Chilean Patagonia, I was impressed that even the most isolated communities now have 4G and the village general store has a card terminal. In Finnish Lapland, too, where there are almost no people, you almost never lose a mobile phone connection in the national parks, and the shops take cards like anywhere else in the country.