The 2nd direct influence on fashion is…

… Function.  A woman working on a farm in Nebraska in 1870 had different fashion needs than Queen Victoria of England.  When women started working outside the home and playing sports, that changed everything from corsets to hatpins.

Pregnancy and childbirth required adaptation of every fashion style throughout history.  How to ride a horse, since horse riding was the only acceptable form of exercise consistently socially approved for women throughout the 1740-1914 time period, dictated “casual” fashion.

(Portraits:  left, Annie Oakley, and right, Sarah Bernhardt were both performers around 1900.  With the same corsets, the function of their performance made their costumes very different as Annie was a sharpshooter and thus allowed to wear a short split skirt, and Sarah was a stage performer required to adhere to societal rules.  Sarah required all women to remove their hats during her performances so people sitting behind them could see her – yet another example of function vs. fashion).