Odd Couples

I was walking down the street today, enjoying my last week off before classes begin and noticed something rather interesting. Most couples that I encountered were not what I would call on the same level ...physically. In almost every situation one person was substantially more attractive than the other and that seemed strange to me at the time. To clarify, I'm not as superficial as you might think after reading this post and will be the first to admit that I prefer other qualities that are definitely more important than appearance. However, I've always subconsciously divided people into 3 distinct categories in terms of appearance: 1. universally attractive 2. universally unattractive 3. The middles which could float either way depending on the person.
You would think that the universally un/attractive people would naturally gravitate towards each other. Furthermore, it has been scientifically proven that we like people that happen to look like ourselves, but it just didn't seem to work out that way during my walk. Maybe the unsuperficial qualities about a person trumps the superficial in most cases, which I really hope is true. If that's the case then I'm not sure why American culture is so preoccupied by outward beauty. Do you even think the people in the relationships realize that either they are the pretty or ugly one? That's seems a bit harsh, but this is my blog and I didn't feel like rephrasing haha. Anyway, I'm just curious to see if any of you know why this may happen...