I was raised a vegetarian by my parents, who both switched over to vegetarianism before meeting one another. My mum already had two boys she'd raised vegetarian, so naturally my brother and I were also brought up vegetarian..
My dad's still a vego of course, but all 3 of my elder brothers "switched over" around puberty.
I think it's partially because of peer pressure, it was hard during school being the only vegetarians and I imagine it would be similar in the workplace or out with friends. Personally I never considered switching cos meat tastes gross and etc. but boys often have a different way of relating to one another, with girls if you stick to your beliefs you're admired with blokes sometimes it's different, they like to one up each other and there's always someone on the out.
I think another reason there's not as many guys that switch over to vegetarianism is that guys don't like to question themselves, or be questioned on their behaviour. If you ask a guy about something he's done, or offer another opinion, he'll often get defensive. That means they're less likely to be all "oh, maybe I'm wrong for eating meat" and change their diets.
In any case, I know many male vegetarians and vegans. Often I'll realise someone I know also doesn't eat meat merely because we'll both be hungry at the same place at the same time. It's not just females who don't eat meat, maybe just your experiences have been skewed?