What is fashion?

Answers on a sealed down envelope or a postcard, please.
When I was taught to sew, and put zips in, I was told they should be as hidden as possible. Well put in zip should barely show when the garment is worn.  Even the brass zips on jeans and zips on men's trousers should be concealed.
So, why do so many ladies dresses and tops these days have zips sewn in on the outer edge of the garment?  I wonder if the quality control found that one machinist just couldn't get the zip right, no matter what they did?  Or maybe the designer them self was not good at putting zips in, and decided to sew it in on the outside of the garment?
Whatever gave rise to the "fashion" of very visible zips, I hope it ends soon.  To me it looks shoddy, or that the wearer has the garment on inside out.  Another thing makes me wonder what sort of nutter thought that brass zip, when exposed, would make a good addition to a ladies dress or top, especially when the fabric is quite a delicate fabric?
I know I don't follow fashion trends myself, but it really does spoil the look of the clothes from behind, and I hope it dies out as quickly as it surfaced.