No, it's not disappointing, actually, it's "we've learned from experience"
. We have been organizing these meetings for over 3 years now, and our experience is that most prospective attendees usually have some kind of social obligation on Fridays and Saturdays. Sometimes we start meeting around 3 PM for a late lunch, other times it's a dinner. You can't ever make it right for everyone. We have even been alternating weekdays and even the weekend of the month, to make sure we could offer people with all kinds of work schedules a chance to come.
Most of those who attend also live within about an hour of the venue, so Sunday is usually not too much of an issue.
Hope you can make it!