Why is it that, in American society, people find it attractive when someone displays overt characteristics that are not associated with their perceived gender?

I am a female nerd and I place myself firmly in feminine gender. Often, when I play trading card games widely accepted as a masculine activity I am told by the male nerds that they find this very attractive. In fact, I started dating my current boyfriend because we met at a magic draft and he thought it was really cool that a girl was playing magic just because she wanted to and not because she was there with a boyfriend or a brother. I also know a lot of fathers who love it when their wives are working and they stay at home with the kids. Additionally, I often hear from women that they love when a man cooks or does laundry on a regular basis.

In this day and age, gender roles are still pretty rigid in some respects in American society so I wonder why it is so attractive when someone “breaks” the traditional gender mold in some way or other.