In the last few years or so Splinterlands introduced LITE accounts, those don't have a spell book and are completely free to play. I don't think LITE accounts by Splinterlands actually have a HIVE account like the normal Splinterlands accounts do.

The charts give an impression that 2017 and 2018 were the years where there was a major momentum and HIVE adoption, after that if we exclude Splinterlands pump during the play to earn narrative pump there is no real adoption momentum...