Time zones!
May sound daft but I've only seen a few that have in mind non US based surfers. Each time I've been to live sites I've found that unless I get up at 3 in the morning I'm going to miss the show and can only watch the archives. I'm in Europe and I'm sure there's loads of folk around who would tune in and join in if the shows were more suited to non US times as well.

Oh - good schedules too, I've recently been to several that have no info about what's on and when.

L