Guess I'm Severus Snape then. I'm single because:
1) People don't like me
2) I find ordinary people insufferable
3) I have a very particular type that is really hard to find IRL
4) I actually have some self-respect and hate being reliant on people
5) I'd rather not deal with the emotion damage of being tethered to another person
6) I've had some really messed up relationships in the past and have horrible luck