Why did soldiers shave their heads in ww2

To be honest i wondered why too but they did because to show unity, so no one looked different, made it fair so no one can make fun of each other's style, and also to show respect to the flag without crazy hair designs to disrespect it.

Shaving your head would help prevent Lice, It is easy to take care of, and helps you stay a little cooler if you were serving in a hotter environment. Also, it helps prevent hair from becoming a problem. (ex. A guy hates this other guys dreadlocks.) If everyone has the same haircut no one can get jealous or angry at another dudes haircut. 

Hope that helps!
-Chris

And this too use this if needed