"Every perception is to some degree an act of creation, and every act of memory is to some degree an act of imagination."
-- Gerald Edelman, Second Nature: Brain Science and Human Knowledge
40 More patterns of Anki use42 More patterns of Anki useMore patterns of Anki usePart I: How to remember almost anything: the Anki systemAugmenting Long-term Memory2020-09-24Journal
My own personal suspicion is that there are three main factors:
In experimental research on memory, people consistently underestimate the gains that come from distributing their study in a manner similar to Anki. Instead, they prefer last-minute cramming, and believe it produces better results, though many studies show it does not.
The psychologist Robert Bjork has suggested\\Robert A. Bjork, Memory and Metamemory Considerations in the Training of Human Beings (1994). the “principle of desirable difficulty”, the idea that memories are maximally strengthened if tested when we're on the verge of forgetting them. This suggests that an efficient memory system will intrinsically be somewhat difficult to use. Human beings have a complex relationship to difficult activities, and often dislike performing them, unless strongly motivated (in which case they may become pleasurable).
Systems such as Anki are challenging to use well, and easy to use poorly.