> Hmm that sounds a bit shallow and materialistic tbh.

It is. But the diamond cartel's marketing (at least in the US, I won't speak for other countries) has been so good since well before I was born that diamond = love, romance, relationship, marriage. For many, many, many people, there's an inextricable link between the two.

It's super lame. But it's how it is. Hopefully that's already changing.