I think it may stem from being kids. A lot of lasses are encouraged when it comes to stereotypical girl stuff so when they get older they stick to what they know. I have a daughter and I can't explain why but, i wouldn't want her to ride trials as its dangerous but if I had a son it wouldn't bother me so much. I don't think anybody I ride with would be bothered about riding with a girl, in fact most of us have been beaten by Donna Fox at Tyke trials.