It is hard to know when the first belt was invented, but it is safe to say that it has been mans primary accessory for most of time.
Throughout history belts were used to hold many different garment types close to the body, as well as to secure accessories around the waist. That is until the first pair of pants came along in 3000 B.C..
Fast forward to the early 1800's when the first modern day trousers were created. However, the first trousers were designed to be very high-waisted, so much so that the belt was no longer a viable solution. So the suspender was fashioned as a new functional solution.
As time passed, new trouser styles were designed to sit lower on the waist, which once again called for the use of a belt. However, modern history has shown that while fashion trends changed, suspenders were the preference of the aristocracy, while the belt was considered a casual accessory for the common working class.
However, all of that began to change around the turn of the 20th century when the Duke of Windsor began wearing a belt with his suit trousers. At the time, it was a radical fashion statement for a royal to make. Incorporating such as "common" accessory into his "aristocratic" wardrobe. But by this time the Duke's fashion sense was already legendary and his new "belted" look began to trickle down amongst his loyal subjects, across Europe and eventually making its way to America.
Valerie Steele of the Fashion Institute of Technology adds, “whether or not suspenders are more functional than belts is really beside the point. It really comes down to people thinking of clothing as function or fashion? The research has shown that fashion has always been about much more than function, and throughout world history people have used fashion to signal messages to other people.”
So why do we wear belts? Because the belt is the perfect combination of function and fashion.