SebastianThere are probably as many reasons for this as there are sands on the beach. They retired from writing. They lost interest in the genre. They went to another site (I've abandoned three sites in the last year and several others I've never returned to). They got busy with work (I did not write anything for nearly eight years). When I first joined here I sent in all my old stories because I saw this as sort of an archive after Geocities folded, but then I started writing again. Maybe they don't feel their stories are popular (my own popularity has fallen off a cliff lately. I just checked--3 hits in 600 reads--that's spectacularly bad).
Sebastian:
But...some of them have also, not logged in for a few years. They aren't reading any stories.
I have to tell you, I don't have much time to read stories if I'm going to write them. Every now and then I do, but I frequently stop reading if I come to something that turns me off.