In the old days, when men were males and women were females, manufacturers made only two kinds of bicycles – one for each of the two sexes.
The male type had a horizontal bar in the frame for added stiffness – as usually it was also often used to carry heavy loads. That meant that if a lady wished to ride this bike, she would have to lift up her right leg high and over the seat in order to mount it. Well, back then most women wore skirts, and thus executing such a high-flying kick would have constituted a major public scandal.
Hence, the female bicycle was made. This one had the horizontal bar re-configured into a Vee, allowing for a more elegant and dainty manouevre for the ladies.