Still they go to the theater, concerts, museums... So blaming new technologies isn't it either. You'd have to erase a huge chunk of cultural events and places for the circuses to rise again.
They're from an era where they were the only entertainment that actually came to you, to your little shitty town where nothing happened ever, where a rogue cow was the stuff of legends. Things have changed, people had TVs, and games, cities grew, and circuses have become more and more obsolete and out of place. That's how it goes...