The point is, changing spouses is expensive if they all want a diamond ring. So that custom is a shield against heavy spouse changing. The whole marriage thing

The point is, changing spouses is expensive if they all want a diamond ring. So that custom is a shield against heavy spouse changing. The whole marriage thing is also extremely expensive. I suspect for similar reasons - so that people think twice before throwing it away. In that case they also have angry friends and relatives who invested into expensive travel and presents and probably wouldn't be too happy if it was all for nothing.