The Strange and Curious Tale of the Last True Hermit (2014)

It kind of just boils down to it was easier for him to steal and that is kind of the crux of the matter in this case. It's hard to see him as some sort of noble nature man when he is eating a diet of stolen snack cakes, yet in other areas what he did was quite impressive. It's a fascinating case, thank you to OP for sharing it.

He was remote, but not quite that remote. At least in his mind, he knew he always had to fear getting caught and be as camouflaged as possible. Heck, he didn't even allow himself a fire.

These sort of constraints make some of the primitive technology quite a bit more difficult to utilize.

Not to mention that he was relying on stealing books - the folks he was stealing from needed to be interested in such things. In their (assumingly) middle class homes, I can see how that might not be in their libraries.

It is extremely difficult to maintain a caloric surplus in the wild with primitive technology. This is dependent on your environment but the places where this type of survival would be easier are also nicer to live in so they've almost all been developed.

This video lays it out pretty well: https://www.youtube.com/watch?v=iAdl63XpXX8