I don't tell many people in my life how much I read manga or watch anime. A few reasons...
- People (in my country at least) don't give the medium enough respect. I have very few friends who read manga, and only a handful more watch anime.
- It's seen as "for kids" by a lot of people (feeds into the first point)
- I couldn't be bothered having to talk about it to some people (same applies with other habits though)