And while not explicitly stated in those exact terms, that's probably EXACTLY what this sign is for. But they probably cover their legal bases if they say sll dogs, in case a non-service dog bites them. Then the airport has a sign "What did we JUST say???"

I work at a different airport, and while I can't say I've ever seen a dog attack someone, I CAN say I've seen people get so drunk that they take off all their clothes at the bar. Then get arrested for "singing kareoke onstage". Except there's a few key pieces of information. First off, they had no stage. She was just naked singing while standing on top of the bar. Like it was coyote ugly. Also, the bar didn't have a kareoke machine, it had a keno display. And there wasn't even any music playing. She just got up on the bar naked and starts a drunk rendition of "allstar" followed by most of "walking on the sun" by smash mouth before the cops showed up and arrested her. Bonus points to the cops for letting her get off the bartop on her own. She used a bar chair to get down, and the top of the chair swivels. So she fucks it up, the chair swivels, and she eats the ground HARD. Like.....pretty sure she had a concussion after that. She was definately bleeding from the back of her head. As someone who has a lot of downtime, and just people watches, that was definately my favorite day for people watching.

Entertaining story aside, my point is.....people are dumbasses. She never got to the point to even try to board the plane, but I assure you, she would have been denied. And she's not alone. Most people keep their clothes on, but a LOT of people (looking at you, spirit, and frontier passengers) drink WAAAAAAAY too much.

So I could fully see a situation where a drunk guy insists on petting a dog that doesn't want to be touched by a drunk guy. I could then understand why a dog would then bite him. And now we understand this sign.