There really is a purpose to Kirk's tomcatting ...

A guy named Matt Bailey did a statistical analysis of the Red-Shirt Phenomenon. You know, the phenomenon wherein if Captain Kirk beams down to a planet with an away team of four crewpersons, one in a gold shirt, two in blue, and one in red, we all know the guy in red's toast. This analysis is part of a seminar he gives on how to give statistical data in an engaging, easy-to-understand way. Go read the whole thing, even the second half on how to present the data--it's so worth it.

Anyway, he discovered a very interesting fact: a redshirt on an away mission has a 53% chance of getting killed. But a redshirt on an away mission where Kirk "makes contact" with a local female, that possibility falls to only 12%. In the words of Matt Bailey, "We can reliably improve the survivability of the red-shirted crewmen by only exploring peaceful, female-only planets (android and alien females included)."

So that's why he slept with everything in a skirt. He was thinking selflessly of his poor redshirts ...