It's about more than the junk the programs offer. Some of which you'll wanna put in the book.
I started doing it in SDM school and we taught that from day one. You want a book for each weapon. It was the single most effective and inexpensive way to efficiently improve shooting AND to learn specifics about how a particular system works in any given environment. Ie, it helps you learn the weapon (helped us track what they were learning and fix problems). Not a single shot is wasted this way and you get the most out of each shot. I also use it to keep a shot record in the field that I can translate back to the shot record in the shop (that way I don't have to tote around the shot record or risk losing it, which I've done).
Besides keeping track of things like weather and ammo details, you wanna call your shot and make an x for that. Then put a dot where the actual shot went. Or use different colors or whatever. Ideally they'll overlap, and the more you practice (in general and with the particular weapon) the more you'll see that happen.
It lets you track any changes, to the weapon or yourself, ammo, parts, position, whatever, whether they're making it better or worse.
You can buy 'em or you can make 'em. We made ours based on NM score cards I think (I recommend printing them on that green waterproof paper and getting a pen that'll work in the rain, "rite in rain" I think?). We had different pages for 100-600m in 100m increments with the particular target drawn out already, so F, E, A or B. Boxes for things like temp, wind speed and direction at different distances, etc. Without FF barrels, using slings made a difference on the groups and it was nice to know those groups shifted approx. 6MOA left.
When you keep good records it'll let you know EXACTLY what to expect from a weapon and allow you to track your own progress and eliminate bad habits or other issues along the way.