As anyone who has published a fantasy book knows, or even people who have thought about publishing one, or people who have read Orson Scott Cards' book about writing science fiction, or even people who have BEEN to fantasy conventions are aware...there are panels where writers give talks. There are classes conducted by writers. There are readings by writers. Writers sign autographs.
All of these things are generally free with your registration for the convention and they are pretty fun to go to. They are even more fun for the writer.
Why do writer's do it? Free convention registration. It's fun to feel like a celebrity. It's cool that someone gives a crap what your opinion is. But the primary reason they do it is to promote their books.
This is true whether the writer is self-published or traditionally published.
Green is doing some panels at the upcoming Con Nooga, but I haven't been prolific enough to do any right now. I'm targeting next year, but I was discussing the panels with the director of Con Nooga and he told me that many traditionally published writers refuse to be on a panel with self published authors.
I'm a bit baffled by this. I've had experience in both realms so I consider myself a fair and balanced representative.
It would seem that both authors are there for the same reason - promote their book. The self-pubs look up to the traditional authors. It would seem it would be fun to be on a panel with a self-pub and help them out a bit. I think this issue will arise more in the future than it has in the past as more and more avenues to publication become available.
Self published authors now might have used a subsidy press, a POD publisher, or they may have published solely online or through Twitter or You Tube.
My take on the whole thing: If you are an author, do some panels. If you are a traditionally published author, stop looking down your nose at people who chose a different path. Write a lot and write often. Go to conventions even if you aren't a guest. Meet your audience.