It's totally for the purposes of Exposition, in my view. A Faire should be more than just booths, beer and boobs, not that there is anything wrong with those. To work, again imho, a faire has to have Characters. If you're visiting a fictional village, the visitor has to know who lives there, and what's going on in the village in order to get the most out of it. The opening show should give the audience the flavor of the faire, introduce the main characters, let them shout and bump against each other, give loud toasts, huzzahs and God-Save-The-Queens. Then for the rest of the day...enhanced by any other shows, when these characters go bumbling by (IN character, hopefully) people go..."Oh, that's the Lord Mayor" or "Oh, That's Sir Walter Raleigh". If it's just a guy in a fancy costume, it's just a guy in a fancy costume. Opening shows set up the story, which is continued throughout the day. it's Subtext. It's Context. it's the Text.

I think it is a nice thing to have an opening gate show but it is not necessary for the customers to have a good time. I believe it evolved as a way to keep the early audience entertained and it does help with introducing certain characters. I know that Bristol has a scenario, a running story that runs through its shows and street bits. On one hand it is kinda cool but I feel the issues outweigh the positives.

In order for you to get the full bang for your buck out of the scenario, you have to be there at the front gate. If you miss the set up, you are a bit lost when you see the other pieces. Now they do list the scenario in the program and you can enjoy the shows as individual units but there are a few bits that leave you cocking your head and going "huh?" if you don't see the opening gate.

The number of customers that see opening gate as compared to the rest that come in through out the day are small. I would guess 10% (on a large day) and less. To me that is a small return for a ton of work. If the show is more general, it doesn't matter if you miss it. You still pick up on the flavor and will see the characters introduced in other shows.

When I was a customer in Agoura I never saw a front gate show, nor a Mayors Show, nor a Queens Show. They just didn't interest me. What did I make a point of seeing every time I went? Sean & Dave, Josephs Magic, Reduced Shakes, Bob & Gypsy, the Joust on occasion and the Queens Progress. That was it. I always had to get a Falstaffs Delight (ice cream confection) or a turkey leg or chicken. Mostly I hung with my friends, shopped, did our early version of LARPing and watched Drench A Wench. We got that the Queen was here. Did we care if there was some story involving Drake or the Spanish or Robin Hood. Nope, not at all.

I had the pleasure once to see the opening show. Even though my daughter and I have been to Faire a few times and have met with cast members I feel it adds to the experience.
I've overheard people say "we've seen it all, let's go home" (this would be my non playtron husband too)
Faire is about it all, including the opening show.

I've been doing faire, mostly at RPFS for the better part of two decades now... and I have never seen the opening show.

The pictures Richard takes of it and his description of it have made me want to change that, though. So next year I may see if I can sneak away from the booth set up long enough to see what all the fuss is about :)