I saw this graph on I Love Charts and I had to stop and think about it for a minute.
I'm not sure if I agree! On one hand, guys you can't have naturally have more allure than the ones you can. (Well, as much allure as a normal dude who likes sports, has had the same best friends since middle school and drives a shitty car with fucked up brakes can possess.)
On the other hand, if a guy is in a relationship, I'm not like, "Oh wow! I can't wait to boing his brains out." However, if he's a good boyfriend, I might think, "I want a cool boyfriend like him" because I'll see him acting rad. I'll observe him sending his girlfriend texts in a timely manner or picking up food for her while we're out because she's home sick and he thinks she'd like ice cream. When you hang out with single dudes, you don't really ever get to see them in "relationship mode," you just see them in "single dude mode," which--newsflash!--isn't as much of a turn-on.
Guys in relationships act differently than when they're single too; there's less pressure when they meet a girl because it's not like he's trying to land a woman or anything. Therefore, he might act more confident and we all know that confidence is sexy.
I don't know. What do you think? Tell me in the comments!