Around 1984, I worked for a Unix workstation manufacturer named Callan Data Systems [1]. Our workstations were 68k based and ran System V.

Except for one that was sitting in a corner of the main office, which I noticed was running CP/M-68K.

I asked around and found out that this was for the accounting people. It wasn't because they needed some accounting software that wasn't available for Unix. Everything they were interested in could easily be done on Unix.

So why did accounting choose CP/M-68K?

Because they assumed (correctly, it turned out) that in a company where all the engineers were Unix kernel hackers, running CP/M would keep all the engineers from messing with accounting's computer.

[1] https://en.wikipedia.org/wiki/Callan_Data_Systems (BTW, Wikipedia says Callan was founded by Dave Callan. That's only partially correct. There were actually three equal founders. They could not agree on a name for the company, and it got to the point where the only thing stopping them from starting was having a name to put on the paperwork. One weekend the other two founders went away on a hunting trip, and when they came back Callan told them he'd picked a temporary name and filed the paperwork, and they could change it to the real name later when they came up with one. They never did agree on a "real" name, and so the company retained Callan's "temporary" name, Callan Data Systems).