I think boys spit for the heck of it, but I never see girls or any women do it. I remember trying to spit for the heck of it when I was a girl, but it just didn't do it for me.
During baseball season, lots of people eat sunflower seeds (down here anyway) and they're all spitting the shells all the time. I refuse to partake.
My mother taught me it was impolite to spit, so I passed that on to my sons, and they don't spit like some of their redneck friends. I'm so glad.
Karen