As someone who does backpacking, a few reasons for bringing power sources:

- A satellite communication device. You don't use them for internet access, but it does allow me to send my location and a small message so I can let an emergency contact know where I've made camp for the night (and a lack of a message means I'm in trouble). It also enables me to contact search and rescue if I know I'm in trouble.

We did have to use it once when my sister lost her footing and fell of the side of a mountain and shattered her leg. (full recovery, thankfully)

- GPS receiver. I've shifted to using my phone as my GPS unit (with Gaia GPS). Trail GPS units have been subjected to planned obsolescence in a bad way, many will only be supported for a few years now, after that you can't load maps into them anymore. Might as well use your phone and Gaia works offline. Although you do learn that modern cellphones really, really hate being offline for weeks on end and random things start breaking down.

The latter was super important this year. With the budget cuts to park services this year in the US, many of our back country trails are in worse disrepair than they usually are. There were multiple days where the only way I knew I was still on the trail was to follow the dot on my GPS and look for the occasional cut log...

Rechargeable headlamp is another one.