Yea, I've noticed the trend for a while and seen it in other areas too. It's similar to some men's "styles" which include extremely baggy and saggy jeans and double X large shirts on guys who could fit in a medium. While women are wearing everything skin tight all around. Where I live (college) men's shorts usually reach somewhere just above the knee. Women's shorts usually reach somewhere slightly below the crotch. I was walking behind a girl at school today whose camel toe was clearly visible through an extremely tight pair of jean shorts! The new men's college basketball uniforms are so outragously long and baggy it looks like the guys are wearing skirts. Real cool.
**In the following, I will not be refering specifically to YOU or anyone you know, so before you even try to play the "offended card" on me I'm telling you now, my following words are generalizations**
Anyway, I'm not sure all the reasons why it's this way for each individual, but I suspect it may have something to do with the differing roles men and women hold in society. Women are cast more as sexual objects while men wield most of the power. Attractiveness in women comes from their looks. Attractiveness in men comes from their power, status, or money, etc. It comes down to what attracts the opposite sex. Men value looks; women value status. Thus, women are more likely to wear revealing clothes in an attempt to attract men. Men can afford to be modest as women aren't as attracted to a fine ass as much as a fine career, confidence or stability. Further, the women's looks represent fertility and child-bearing fitness (large breasts and broad hips on a trim waist) while the men's status and confidence represent supportive fitness or the ability to provide safety and supprt for the mother and her child. Ultimately, these are all just generalizations or averages, and there are plenty of men and women who defy these observations.
There are several perspectives from which to approach the idea: cultural, sociological, psychological, and my favorite, biological or evolutionary. They all say the same thing from a slightly different angle, which is something similar to what I laid out above.
But what's really wierd to me is how the trend is increasing lately. As you mentioned, the "old style" men's shorts were much shorter. In my opinion part of the new trend is due in part to the increasing prevalence of hip hop culture which accentuates the sexual symbolism of women and the dominate power of men. Rap videos are notorious for their scantily clad women, while the men in the same videos wear the baggiest and saggiest of any clothes I've ever seen. Yet, there very well could be many more explanations that I've over-looked. Lot's of non-hip hop styles follow the same trend, but few would deny that hip hop culture has been a trend-setter.