there is usually a disclaimer at the arena and on the ticket telling you that by attending the game/walking into the arena that you may be photographed/video tapped.

And there is an expectation that you may show up on the kiss cam or dance cam or even on TV as it is a filmed event.

At an airport, there's an expectation that you may unwittingly photobomb someone, or that you will be on CCTV. But there's no expectation that a professional photographer will take candid pictures of your 3 year old.

I took a photography class in college and we had a full class discussion about the ethics of candid photos. I feel like when you take them, you should tell someone immediately after you do, let them see them and delete them if they ask. It's not cool to just photograph someone in an "official" capacity without asking for permission to use their image.