Usually, their expectations are way too high. They join, expect to make a lot of money, don’t make a lot of money (or any at all), then quit.
Or, they just can’t figure anything out and get frustrated due to the complexity of the system and the horrid user interface.
Those are probably reasons #1 and #2 for the failure to retain users.
Generally I believe if users expectations don't meet with what the product is actually able to offer, it's not only a users mistake. Then it's rather a lack of communication.
Why do people expect getting rich on steemit? 1) Because there are a few who're filling their pockets on a daily basis. 2) Because they weren't educated before joining the whole thing.
Have you ever seen the welcome page of steemit? After opening that page I had actually no more questions... 21st Century, blockchain technology, and then... a loooong text, haha! The most important advice comes at the very end, so I wonder how many people have even read it?
Yes, that's it. But nobody knows.