I can think of three or four good reasons: 1. To prevent buying duplicates. I own enough books (on the order of thousands) that I can't remember all the ones I

I can think of three or four good reasons: 1. To prevent buying duplicates. I own enough books (on the order of thousands) that I can't remember all the ones I own, and occasionally buy something only later to discover that I just bought a 2nd (or 3rd) copy. 2. Insurance purposes. If I had a fire or something I imagine I might need the catalog, photos, etc. as part of my claim process. 3. Related to (2), but if I had to replace a substantial portion of my library, it would help if I had the items in the library cataloged. 4. Locating books. I have enough books jammed into my apartment that I sometimes struggle to locate a particular one. Or even remember if I own a particular title at all or not (see (1) above). A catalog, with notes like "In living room, on bookcase A, shelf 2" or "in office, bookcase Q, shelf 4" would be a huge benefit at times. Even more so for the handful that would fall into the "Boxed up and moved to storage locker on 08/16/2019. Box labeled BR549" category or whatever. I have 3 tall bookshelves of books but don’t really feel the need to catalogue them Well sure. If I only had 3 bookcases of books I don't know if I'd bother either. But when you get into the multiple thousands of books, it becomes more important.