Fashion Wiki
Wearing a T-shirt under a crewneck is a simple style choice that can significantly affect comfort, hygiene, and the overall look of your outfit. Many people prefer layering because it keeps the crewneck cleaner, makes it feel softer against the skin, and provides a smoother silhouette.
Many crew neck T shirts are designed with a straight, unshaped cut, which can make the body look boxy even when the size is correct.