I guess they didn't buy the optional network software.

I remember working with this engineer writing in the lower level TCPIP stack on the deck - maybe in Fortran? Anyway, he didn't understand why he wasn't getting all the data transmitted and while I was no expert in TCP/IP, I was already familiar with packets and maximum segment size (MSS). I remember being impressed that he banged out a network stack in a couple weeks.

Baseway, and various other industrial control systems that also ran on VMS and related, tended to either use DEC-suggested (DECnet) protocols or implemented custom Ethernet-layer ones