Cupid's Reject

This is someone who never finds love. Not because of any shallow reason, such as being ugly. Not because they're rude, or clingy, or too eccentric. Not because they have no life, or poor social graces, or because they have no job.

They are that often ignored mysterious minority who are perfectly normal, adjusted, and accessible whom - for some reason we can only conjecture - never find someone interested in them romantically. There is no good reason, as they may even look for it actively, and it is worthy of contemplation if nothing else.

"That's Bob. Nice guy, works hard, gives to charity. I heard he's never been kissed though," "No way. There must be something wrong with him," "Nah. He's just one of Cupid's Rejects."