Hello, grab a beverage as I'm going to talk about the Galactic Empire between the years 19 BBY and 4 ABY (after the battle of Yavin). During this time period the Empire had a strict culture in the beleif that humans are superior to other species. This racism also carried over to humanoid females and a distrust in droids. This culture lead to policys and prejudice where humans became the only race capable of rising to the pinacle of Coruscant's political powers. Aliens and humanoid females were completely blocked from the higher ranks of power within the Empire's military and government. This went as far as having Admiral Daala a story book character of the Imperial Navy being promoted in secrecy by Grand Moff Tarken. Daala would be considered C-Canon, In other words it's on a level lower than the films, but equal to the books.
The only female stormtroopers known are based in a far later time period (137 ABY), Jes Gistang is the only named female stormtrooper and she wears armor shaped to her femenine figure. Jes Gistang can also be considered canon however being the best example we have we can accuratly assume if there were female stormtroopers in the time period of the original trilogy they too would wear similar armor and not armor fitted for a males build; like the stormtroopers we see in the original trilogy.
Given that the Empires main fighting force during the Empires rise was made up of clones I beleive the racism and hate towards droids, alien species and even the anti humanoid female culture to be rather realistic. An all humanoid male fighting force. If you have seen the original trilogy you will notice not a single alien or woman aboard any Imperial ship, in any station, nor fighting in any battles, besides hired help and prisoners. It is also noteable that the only droids used are for reconnaissance among other tasks, they are never witnessed playing a fighting role in battle alongside Imperial forces.
Hope this helps with better understanding of the Galactic Empire and their racial stance, thanks for reading <(o.o)-b