I never logged dives back in the old days, and when I first heard this dern newfangled thing about logging dives I thought it was pretty dumb.
But I started doing it anyway, and guess what? I learned a lot of important stuff.
Even in a pool (sometimes, ESPECIALLY in a pool) you can learn things like fitting your gear to you, ideal weighting, trim, your air consumption, kick cycles vs distance covered, and how your gear works (or doesn't). I log it all.
I often go back to my logbook to find out when I started using a particular piece of gear, how much weight I used with that wetsuit, or what my SAC rate was under those conditions.