I've long since given up wondering why one person goes out/lives with another..I try to just accept things as they are.
I do believe that there are so many people in the world that to find someone that's right for you means you have to get out and meet the rest of the world.Being shy about it is a waste of time.So what if someone rebuffs you?It's not the end of the world as there are millions of people to choose from but you have to look them in the eye to see them.Thinking someone is too good for you is silly or thinking you are not good enough for them is just as daft.
So deciding just on looks alone is one way to sort people out.However if you expand your search(as in google) you can find someone who suits you down to the ground.
BUT YOU HAVE TO TALK TO THEM FIRST.
If you are looking for a partner that is.
If you are just after sex I guess you only have to get 'lucky' once.