How much of this is influenced by people just paying more attention to those around them when they see someone dressed as Batman?
Like, personally, when I'm on public transit I go into full disassociation mode. I wouldn't even notice a pregnant woman because I'm trying my best to ignore everyone. But someone dressed as Batman would snap me out of that. Its hard to ignore someone dressed as Batman, and once you focus on him, you start focusing on other people as well.