Etiquette for inviting married couples

Recently my wife was invited to two weddings where I didn’t know the person getting married. She got excited about it and wanted to pick out a dress, etc.

We both assumed I would also be going but in both cases my name wasn’t on the invitation and when she asked she was told that because of cost they weren’t allowing a plus one. This led to a really awkward situation where I dropped off and later picked up my wife from the wedding (so she could drink a little).

Is this proper etiquette? I can’t imagine inviting only one half of a married couple. I get not wanting everyone to bring a date but this seems different.

In both cases we greatly reduced the amount of money we gifted the couple so financially they probably actually came out behind by doing that. Yes, we were both a little hurt and did that out of spite.

Update: This was in the US, the weddings were fairly large, and they were both friends from college she isn’t super close to anymore. I was excited to finally meet people I had heard so much about.