Just off the top of my head, what if I want to use reddit mostly to talk about mundane things like local events in my city or technology and don't really care if that ties back to me, but I also want to ask about embarrassing health problems or just weird shit and I would rather not have that tied back to me? I should have no options without everyone in the world being able to easily find out about it?

If some sites like Facebook want to be real-name only, that's fine. People can use Facebook for that if they choose. But don't ban alternatives for people who want alternatives.