Why? Because we were traditionally raised by society that says "no, you can't do that". Takes generations to overcome.

Even when I was in college, "girls" were told not to apply for the jobs for the men. The job board at the university financial aid had a line drawn down the center of it. I remember looking at that board for a job... on the left top was the label GIRLS, on the right, MEN. The jobs on the left were about $1.60/hr. The jobs on the right were $3 to $4/hr. The descriptions were things like, "looking for the right man as assistant manger". I bucked the trend by applying for a groundscrew job outside for the horticulture department. I was paid $1.68/hr. I found out at the end of the summer that the boys I worked with were paid more.