It's funny how many people join the site and only play Live games, that think that Live is all you can play here. They don't know they can play correspondence chess here, what it is and how it works. I've met a lot of people who joined some of the groups I am in via invitation or via applications and also met some in Live that I had to educate on correspondence chess and also team matches, how they worked.
When new members join the site are they on joining presented with a video that talks about all the features of chess.com? Explains how groups work, live chess, correspondence chess, extra features/benefits if they become premium members? I think there should be if there isn't.
I haven't tested it out (synchronous vs. asynchronous) on lay people, but my sense as a technical (i.e., computer-industry) person from working with non-technical (yet still quite intelligent!) people over the years is that there's a threshold of technicality that doesn't get easily crossed in terminology or imagery, even if the concepts may seem obvious to the technical folks. I may be wrong here, but it's my hunch...
I think this is more true in the computer/programmer world than in any other sphere. when people start talking programmerlese, people's eyes just start to glaze because every other word is something with which they are unfamiliar. I stand by my assertion that most people would be able to easily grasp synchronous vs asynchronous and that the problem lies more in that the term "correspondence chess" just isn't very sexy.