The tradition isn't as old as people think and was literally started by a jewelry company to sell more jewelry. Specifically diamonds, which are not as rare as commonly believed and if not for the false scarcity and misinformation, would be dirt cheap.
It's crazy that even when people are told about this, they usually still defend it. I don't get why the heck any normal person would like the idea of spending a few months salary on a ring. It's such a terrible way to start a new marriage, especially with wages being what they are these days.
Diamonds were fairly rare when we used to mine them in Asia and America. And it's a nice shiny stone which is also very durable.
Then, we found out Africa is actually full of diamonds and DeBeers said "we can't have that!" and started buying all the African diamonds to keep them away to artificially inflate the price and scarcity.
Then we found out we can make them in labs better than the mined ones and DeBeers sai "that's not a natural diamond, you don't want that!" and so on.
The whole marketing about "A diamond is forever!" is to make you think you'll never want to sell your diamon ring, so you don't find out your precious gift paid $2,000 is actually wortth $50.
An EA spokeperson would say "it's all about the experience".
Back before lab-made perfect diamonds were a thing, the DeBeers cartel marketed that they had the highest quality diamonds out there, with the fewest imperfections.
Now they market that the imperfections are what gives it character, and you should avoid the actual perfect diamonds and instead get their (blood) diamonds.