One of the benefits I've found is that it forces me to be brief. I've almost always kept notes and journals in a text format that I store in VCS, but I've found that journaling by hand is a vastly superior experience. It isn't simply about writing. It's about thinking of ways to write what I want more tersely (I'm prone to being verbose), and it's helped me process things ex post facto in ways that writing out the way I used to do simply couldn't accomplish.

I've also started collecting fountain pens, so it's linked to a related hobby. It's difficult to express that it is the entire experience, from the ink, to the feel of the pen, to what words are being written onto paper, that feels the most rewarding. I've also rather deliberately avoided document inks after much contemplation. I figure that the majority of inks I have aren't waterproof; if the journals ever get wet, everything in them will be destroyed.

That's how I've grappled with the ephemeral nature of the physical. Rather than aiming for optimizing permanence, as best as can be done on tangible, material books, I've preferred to embrace its weaknesses with full acceptance of what can (and will) go wrong. I suspect this is also because I have very little intent to ever go back and read what I've written. That could change, of course.