Speaking as a regular person rather than a juggler, I think "the circus" in the US at least is held in low regard because we think of kids, overpriced cotton candy, and parades of animals. The biggest one is Ringling, which actually has a wide variety of talent, but there are so many smaller traveling circuses that just aren't very good.
(I don't like seeing animals in the circus, period. The parade of elephants, the lion shows, even the horse riding shows. I didn't like it as a kid, I don't like it as an adult. It ruins the magic somehow.)
Circus juggling is complicated, though. Most people only see 3-club comedic clown juggling, and aren't even aware there is more technical juggling out there. And when there is higher-level technical juggling in a show, I guarantee 95% of the audience doesn't really comprehend what they're seeing, beyond stuff flying in the air and someone catching it. So at some level, simple 3-club juggling may actually play BETTER than numbers or technical stuff, because the average person can actually relate. And for that, the showmanship is just as important as the skill.
Cirque changes expectations a bit, because every audience member is VERY aware that they're watching performers who are at the absolute top of their game. The juggler isn't filler while they change the set, he's a solo performer on a very exclusive stage. I think that's why Gatto et al fit well in Cirque: They have the audience's attention by proxy, and for their set the entire show is focused on the juggling, instead of a "sideshow bob" activity while you go buy more popcorn for the kids.
Speaking as a juggler, I agree with everything you said about what juggling is to you. It's a hobby, a sport, a personal challenge, a relaxing pasttime, etc. I enjoy watching technical juggling, but I understand what I'm watching. Non-jugglers don't, and let's be honest, watching someone juggle 7 rings from a side view (stage performance) doesn't convey anything about what the juggler is actually doing up there. And without that context, he's just another random circus performer. So I understand why the average observer just doesn't get it.