Everyone was once a newbie, including me, and for this prompt, I will tell you what I think about some newbies leaning hive after a while.
Without beating about the bush, the number one reason a lot of people got here was simple: reward, even before understanding in detail how the system works. Then, when they are finally in, they will begin to understand that a lot needs to be learned and followed before having some rewards, which isn't predictable for each post.
So basically, from my experience, the complexity in navigating the blockchain without manuals or training is one reason why some leave, and secondly, for lack of rewards.
By God's grace, I was a newbie instructor for two years. The founder of the newbies initiative, who is no longer on Hive, once approached me to be assisting him in training the newbies, and I accepted the request and committed my time and energy to coaching these newbies on Hive for two years until this guy left Hive for a greener pasture.
Hive blockchain is not like other social media platforms, which are much easier for you to navigate without much guidance. Here, there are lots of front ends to learn about, changing of keys, managing wallets, converting swap.hive to hive, converting HBD to hive, powering up, growing your HP and HBD savings and interest, and a lot to learn, and trust me, it's not easy to walk on this path all alone.
So for some people who don't have any one to coach, that person could get frustrated and leave along the line.
Secondly, we all know that the rewards here aren't guaranteed, but people are impatient and inconsistent, so seeing those expected rewards becomes difficult before they finally leave with the mindset that hive doesn't pay .
So I suggest communities should make an effort to follow up with new members in their communities. A little class or guide here and there can help keep them until they understand vividly how the system works and take advantage of both its knowledge and monetary values.