In the military, there is little room for "personal expression," when it comes to appearance. Like it or not, the American public often judges the discipline and effectiveness of a military service based, in part, on the manner in which the uniform is worn, and the personal appearance of that service's uniformed personnel.
When the services determine their grooming standards, their primary consideration is to have a neatly groomed appearance while wearing the uniforms of that service. Grooming standards are based on several elements including neatness, cleanliness, safety, military image and appearance. The standards established by each of the services are not intended to isolate military personnel from society. Military grooming standards are designed to be reasonable, enforceable, and insure that personal appearance contributes to a favorable military image.
Below are the grooming standards for the Army, Air Force, Navy, and Marine Corps: