Not Everything Produces Output

In PowerShell’s world, output is what would show up on the screen if you ran the command and didn’t pipe it to anything else. Yes, Export-CSV does do something - it creates a file on disk - but in PowerShell’s world that file isn’t output. What Export-CSV does not do is produce any output - that is, something which would show up on the screen. For example:

See? Nothing. Since there’s nothing on the screen, there’s nothing in the pipeline. You can’t pipe Export-CSV to another command, because there’s nothing to pipe.