An Expensive Tradition
We can start with the Ancient Romans. During this time, men often gave their betrothed rings decorated with keys. The circular ring was symbolic of a couple's never ending unity, the key of protection for the future husband's heart and the unlocking of the bride's dowry. The Ancient Egyptians decided that the ring should be worn on the fourth finger of the right hand as they associated it with the heart. Engagement rings became even more common in the 13th century when Pope Innocent III decreed that a couple should have a waiting period between engagement and marriage in order to solidify their commitment. Thus, the ring came to symbolize that.
Up until the 15th century, the rings were simple, lacking jewels. The first recorded engagement ring actually featuring a diamond was given to Mary of Burgundy by Archduke Maximilian of Hamburg in 1477. But in the following centuries, only the very wealthy could afford bejeweled engagement rings. This changed in 1938 when N.W. Ayer & Son, first United States' first advertising agency, was commissioned to reverse the falling price of diamonds. The company coined the term “A Diamond is Forever,” brilliantly trying together the idea of diamonds and love. And soon enough, even Average Joes were on the hook for expensive engagement rings.
So love it or hate it, the tradition of engagement rings is pretty well-established. And if you're a guy, there's a chance you will have to buy one someday. Just please, please don't spend two months salary on it! If the rings themselves can't go, then that rule certainly should.