You can't compear a institution like Zoos, with a history education and conservation. With a circus, a simple source of entertainment. With no deeper meaning.Wih little care for animal walfare
Well,
@birdsandbats did put it on a shorter explanation, but I might as well say it after spending some time in this.
Before the invention of the television and the advancement of public transportation, circuses were the only way people living in small towns and rural areas got to see animals that are as uncommon as a dromedary. It might not be as educational as a modern zoo bringing awareness about endangered species, but at the time, being taught that there are beasts such as kangaroos or warthogs is still teaching the general public
something. The public still becomes aware of something, therefore the circus has a history of education. Also let's not forget that most modern zoos started as mere pet collections without any "deeper meaning" or any of the activities they self-congratulate over today.
People like you wouldn't even bat an eye if circuses improve their animal welfare because they are doing something that you
don't like.
I'm sure you have heard of Martin Niemöller's "First they came...". If you think that noble modern zoos are going to survive the animal rights rhetoric and the gullible public and government, even after helping them abolish the novel, "cruel","inappropriate" use of wildlife, think again. To expect the banned groups to help the noble, is naïve (although some might sympathize and forgive modern zoos as well).