As-is, many employers will not hire individuals who have certain types of modifications, or can ask individuals not to wear their jewelry or cover their artwork.
Most people in the U.S. have a tattoo or piercing, and allowing an individual to have earrings but not others is discriminatory and hypocritical. Many forms of modification are vital to an individuals beliefs or their self-concept, and by removing them from the workplace, it furthers the stigma that only "certain" types of people are modified.
By hiring individuals based on their qualifications and not by their appearance, it will promote better understanding of those who are modified while also allowing them to feel safe and accepted in their workplace.