I don't know why I thought this was something that people just knew, in particular about the false scarcity of diamonds. When my wife and I got married we excitedly picked out inexpensive wedding bands with an aesthestic we both loved and a symbolically long-lasting quality - tungsten carbide.
Ultimately, we ended up not wearing anything for a number of reasons*, we've now been together more than eight years and our marriage is still going strong in spite of our naked fingers.
I'm pretty sure the rings have no real significance.
* Tungsten carbide is a super hard metal and we got married during a period of my career where I physically facepalmed a lot. We almost broke our fingers on a number of occasions, and the final straw was my wife gently smashing a smartphone screen by putting it down on a counter.