[prithee]

They are valuable the reasons you mention. I'm an avid reader, and sometimes people will ask me a question about a recommendation or what I've read, and I have a complete brain lapse (to the extent it's as if you'd wonder if I read at all). Having a list helps that anxiety. I don't really use the other features, and only settled on Goodreads after the Shelfari "merge".

I do the same with logging film watches on IMDb, which is actually useful because I can visualize exact watch behavior by the timestamps, and using exports I can also query my film history for personal recommendations (select documentaries that are horror tagged I've watched from the last 10 years).