sensitive side, the side that isn't abusive or masculine to the point of being scared of being harmed.. just speculation as I doubt anyone could answer this for you,as I'd think you would know more about it than us, seeing how it is you and others, who don't think the same way 100% of the time.. like drones.
If I could guess, It's because your attracted to guys that can be potential fathers or care givers. For many girls who are looking to have a family, that's what they look for. So maybe that's why. I dunno, I see it as animal behaviorism. Some girls like guys that can be potential family men, and if they can care for something/someone so small, that's a big plus for their sensitive side.