The raw versatility of the T-Shirt makes it incredibly useful. Traditionally, it was worn under a long sleeve button down shirt. Later, it became acceptable for t-shirts to stand alone as a work shirt. Still later, the t-shirt would become a statement or billboard. The uses for Tshirts have exploded in the last few years.
T-shirts started out as an undershirt. Usually white, occasionally blue or black, it served to keep the wearer warm. It also served to keep the outer shirt from being soiled by the wearer's bodily smells. But this is not where the T-shirt would end.
In the early 1930's, men working on farms, in manufacturing and small repair shops stopped wearing the outer shirt all the time. The undershirt officially stepped into the light and became the T-shirt. Workers wore just the t-shirt throughout the day as it was cheaper than the traditional outer shirt. And since most were still white at the time, it was easier to clean. This lasted all the way through the forties as a style of wear.
Then the fifties came, and it was acceptable to wear plain colored t-shirts to school, especially when it was discovered how useful they were in sports. Suddenly, everyone could walk around in a tshirt if they wanted to.
Then the 1960's rolled in. T-Shirts became a billboard to carry your own personal slogan. If you could imagine it, your t-shirt could tell it. Custom printing became a service industry all its own. T-Shirts are now the neon signs of today!