Probably because they're doing something, y'know. People stare at you when your doing something a bit more interesting than standing around talking. Its like pulling out a set of juggling balls, you know what I mean?
I get looks when I put on lipgloss in public, but that's a whole other thing, hahaha.
Personally, I don't think they stare because they think it's attractive, I think they stare because they wonder why we do it. That's why I hate doing it in front of boys, it seems like we're trying to hard, and it's a forgien concept for guys. At least most guys, lots of my guy friends, and boyfriends have told me they don't like lipgloss or chapstick.