Some people don’t get it. “Why Professor Snape?,” they ask. He’s mean to kids. He’s ugly. No one wanted him; he’s probably a virgin. How can anyone find him sexy?
1. Because smart is sexy. Competent is sexy. And you know that’s what he wants in a mate.
2. Because sarcastic is funny. Because bitter tastes good. Because every time he opens his mouth, he delivers.
(And brilliant, bitter, funny male virgins? Enough said.)
3. He’s always there, just when you need him. He knows what you need and how to do it. Being a Legilimens, he also knows what you want. Think about it.