Janie - I don't think it is an easy question to answer.
Why do some people arrive and stay, whereas others arrive and then disappear?

Since becoming a member,I have talked to various people who did not stay, and there have been an assortment of reasons they have given. I'll try to summarise diferent responses with "Reason for Visit" (RFV) and different outcomes.

RFV - to get a question answered.
Result 1 - question answered, so do not need anything else from Mudcat/ I'll visit again if I have another question.
Result 2 - question NOT answered - if Mudcat doesn't have the answer to my questions (must be useless) I'll go elsewhere.
Result 3 - Upset by someone. They ran into one of the rude people (sometimes a member, sometimes a troll), went away angry and have no wish to repeat the experience.

RFV - They have heard about the Digital Tradition.
Result - They want to find lyrics. What they want is in the Digitrad. They are not interested in discussing the lyric (or anything else) so they go away. They may return at some later date.

Some people see themselves as a "Big Fish" in their respective "Pond". They do not like it when they arrive at Mudcat to find they are actually a goldfish in a bowl, and they have just been released into a lake full of bigger fish with teeth.

Some of the regular 'Catters spend time on different forums with a more specialist bias. Other members of those forums may simply have decided that the expertise and interaction they seek is covered by that particular forum and not see a need to see what Mudcat offers. We are a very wide collection of divergent interests, which for me enriches the place, but wouldn't for a musical monomaniac.

I personaly like the Mudcat's "All recent threads on show" format, but it does mean that if you were only interested in reading Blues or only English Ballads, they are not already sorted into little (or big) boxes where one click brings up every ballad discussion. It can be difficult to find a specific topic, (even when you know it is there because you remember contributing to it some months earlier). Thread titles can be misleading, and a forum search can be inconclusive if you choose the wrong search term.
A casual visitor who doesn't know the system can be excused for thinking that Mudcat isn't the answer to their needs.

Perhaps it would help if Max could create a system where threads could be "Tagged" with extra sub categories beyond the standard "Lyric Request"/"Tune Add"/"Folklore" ones, so you could click boxes labelled "Ballad" "Bluegrass", "American", and your search would narrow down to threads which contained all three tags. Of course, even if the database can be modified to include such tags, somebody would have to actually go through threads to tag them, and that would not be a quick process even if some clone or clones were willing to take on the task.

Just a few semi random thoughts.
Quack!
Geoff.