Data brokers like Experian can tie that number to the rest of your profile. Even something like "this is an AMEX" can give you some info.

Where you're coming from and and going to. Your name and home address.

It doesn't need to be 100% perfect in all cases to be useful.

that doesn't answer the question, which is about credit cards.

Then I don't understand the question, but you can probably make pretty decent guesses about a person's income just by looking at the type of credit card and the issuing bank. And definitely if you include credit card billing address. There's tons of databases that translate a zip+4 to a median household income.

I don't know about temporary card numbers, which afaik don't exist where I live but : the data-industrial complex indexes people by credit card numbers so given the number you can get a full profile. Income, etc.