It doesn't in general, unless one plays up a single aspect of themselves to overshadow their other weaknesses. (Ever notice that very over weight women tend to have their make up, hair and nails done to the nines? Same thing)
Of course you need to be sexually compatible but there still needs to be more beyond that. After, 10, 20 years together that great time you have humping in your 20's may very well become strained (especially after kids) over time or worse non existent, so what will you have to save the relationship and bring you back to where you were before life got in the way?
For sake of example, let's say a man thinks that he's got it made with the ladies because of his job (makes good money) and penis and because of this thought process he doesn't put any effort to being a good person in other aspects of himself and it's all about money and sex. It's really the same thing as a woman that only focuses on her looks as bait to a man but doesn't expand any other part of herself (mind, career, etc) and thinks that's all she needs to land and keep a man.
Reality is that man and woman above will hook up because their superficial desires compliment each other but long term it would be difficult to sustain the relationship and they will eventually find ways to resent each other for who they are and for who are not. Relationship breaks down. They're scuba diving together but they didn't bring tanks of oxygen to keep the tour going.
I get it, we are animals so our greatest desire at the core is eating and breeding and very often our choices unconsciously reflect those desires. But at the same time we parade around as a superior species when we behave like we're no farther advanced then apes.
I would like to believe that most of the human population has evolved more than that.