It's not the standard here. In person and in media, there's a table full of wrapped gifts for the bride and groom. While I'm sure nobody would turn down cash, they wouldn't feel as appreciative of it as something that was bought with them in mind. Especially things that they'll still have 20 or 50 years later, and it brings back a memory of their wedding.

> This is a Jewish thing?

Not only, it is normal also in Poland (though it is normal that people give both physical gift and cash).

It's very culturally specific. Definitely not WASPy normal in the US.

Traditionally, people often registered somewhere like a department store or a kitchen goods store. Some of the function of gifts was historically to get a young couple moving out of their parents' houses a start. Of course, these days a lot of people are pretty well set-up before they get married.