I don't think the number of guests matters - it's how long/elaborate the service is. If you're just doing a brief, simple ceremony, there's not a lot of info to fill people in on.
We decided to programs so that our guests would feel more involved in the ceremony and know what was going on. They wouldn't have to wonder who was who in the wedding party or where things were in the order of service (like if they were wondering how much longer they'd have to sit there!)
We also used it as a way to get another reading into the ceremony without actually having to read it - it was just printed in the programs.
And we included a note of thanks to our guests for coming. It was a good opportunity to thank them more than just verbally.
Hope that helps!