There are sooo many stories for any taste on GA, that It's easier for newbies (or anyone that doesn't know where to start) to simply read from any titles in the different "New Story Updates" lists. Then if they catch a story they like, start reading other stories from the same author.
As such, the fact that Dom, or when other Hosted, Promising stop writing/posting for a while, less people will find/read their stories and even less will comment on them.
Personally, I say that forums have their place because it gives the interaction with the author as well as discussion with other readers. That is part of what, imo, make this site special and what first prompted me to actually register to the site.
I would be very curious to know, from the amount of people reading a story what % of them will actually make any form of comments to start with...
In all cases, even more so now with GA.Stories, there are less and less story discussion with the ease of the review, likes and so on. Things evolves we just need to adapt ourselves as well.