Actually, gingham was more like denim and calico. It was practical, tough and could be washed at high temperatures. There was a meaning behind the traditional pattern (these things don't happen by accident, like tartan. We've just kept up the pattern. Girls don't have to wear dresses, but some want to. Some women want to wear bright/pastel etc clothing. I live in dresses over summer. I like pink, in the cultures I mix in, pink is a unisex colour. Women and girls now have more choice over clothing.