I believe these were something like the Kaypro, where there was no onboard graphics...just a serial console. So, no reason to change it, other than maybe some tweaks to the ROM for branding in the admin interface and boot-up.
Sorry. I meant in relation to the vt100 - it was a very expandable machine that served as the chassis for some stand-alone desktop computers sold by DEC.
They sometimes stuffed a computer into the terminal. DEC themselves did this: the VT103 is a VT100 with an LSI-11 (PDP11/23) built-in. The VT180 is a VT100 with a Z80-based CP/M computer inside.
Maybe for backups, or sneakernet. I know one place I worked (the chemical factory I mention in another comment), the administrative offices weren't on the same network as the labs. I think it was a geographic limitation because the two buildings were separated by a 20-foot-tall earthen berm, to protect the admin building in case the lab building blew up.