They aren’t, and our private phones are also connected to the network ;)
But then again, it’s a fairly large organization vpn’d up over multiple locations, with server farms in different VLANs and so on, so the network we usually access when working are in a different subnet.
I do know what you mean though - it really depends on what the company does. Prior, I worked at a company that developed and manufactured hardware cryptography devices - I learned proper security procedures there :) our ‘actual work computers’ weren’t even connected to the Internet, and the unmanaged laptops accessed the same WiFi guests would access that, well, only went to the Internet. Just wpa2.