Because you should never fully trust any IoT product that you don't truly have control over. There's nothing stopping a faulty or malicious update from being pushed out, or their update servers being compromised (see notepad++ recently). So why increase your risk, if you don't truly need it online?

You're missing the point of what I'm saying: You shouldn't have to change settings to know that all your prints are not being sent to a remote party.

Networking filtering as an additional measure - sure. But it shouldn't be required to get sensible behaviour