Why you might ask?
Studies have shown that the part of the male brain that lights up when viewing pictures of people in skimpy clothing is the same that is associated with tools such as screw drivers and hammers.
Here is a video about swim suits and how it has evolved in our society:
http://youtu.be/WJVHRJbgLz8
So when you decide what to wear out the door, think: "How do I want people to view me? How am I representing myself?"