What's the Obsession with Sexy?

I've often wondered why we (people) have such an obsession with sexy. Everywhere you look - someone is marketing the idea that sexy = "happiness" or sexy = "success" or sexy = "sexy mate".

I've often wondered - are people naturally obsessed with being sexy or have we been sold on the idea that being sexy is really important? Feel free to offer your thoughts on this subject in this webpage about being sexy.