If you think about it, a ring is just as unneeded as a diamond. The situation is that a diamond ring has become a social norm. I would bet that if you ask most women whether they want a diamond engagement ring or another type of rock, they will pick the diamond ring by an overwhelming majority. Imagine a woman telling others about their engagement and showing a rock other than a diamond. It would be a disappointment any way you see it. The "diamonds are a scam" reason just won't cut it. The diamond industry has been extremely successful at planting that notion in society.