The catch for me? I'm a self-published author, which for the sad majority of the conference organizers means I'm not a "real" author. I'm welcome to attend as a reader, but not as a professional. "Thank you for interest, but call us when we can find your books in Target." It makes choosing which cons to attend really simple: if the Con welcomes Indies and treats them equal to trad-published authors, then the odds of me participating vastly improve.
Now, there are Indie-specific cons, but it's an author-beware sitch. Too often, they're akin to MLM trade shows, where you're the prey and the "networking" is with vanity publishers, "PR" spammers, and book "doctors." Also unless it's a genre-specific con, most of the Indie stuff is targeted at non-fiction authors. When it comes to those type of cons, the emphasis is on the "con." You're better served handselling books at a local fair.
Locally, there is an exception to the Unwelcome Indies trend. One part due to the genre to which it caters (hello, Romance) and one part to the tenacity of the organizer who embraces the community as a whole. I'm referring to Lori Foster's Reader & Author Get Together (RAGT) that welcomes trad and indie authors for a weekend of hanging out with readers and an open-to-the-public book sales/signing event. It's a pay-to-play event, with conference revenues going to local charities. It is, in essence, a fundraiser more so than a con. Mad props go to Lori Foster and her team of organizers who persevered through all the lumps and bumps over the years of integrating indie books into the event. (The onsite-bookstore had challenges offering indie books, what with the inability to return unsold stock among other issues. Lori and her team continue to revise solutions while offering ones that work best at the time for all.)