In Germany it is not a thing either. Discreet gold/silver rings are much more common. I like it, it is less decadent and you can wear the ring every day.
That's weird, all my SO's friends who are engaged/married here in .de got diamond engagement rings. They also wear a wedding band, and tend to only wear the engagement ring on special occasions..
As we know, Germany is very diverse. Probably it depends on the region and the social environment. I know that in conservative families it is common that mothers give their inherited engagement ring to their oldest son/the first married son for example.
In my direct environment many people broke with that tradition.