I’m familiar with a multibillion dollar international corporation that uses an excel spreadsheet to communicate between divisions.
Not email or slack or teams or the telephone. An excel spreadsheet.
The left column is where one division enters a message, and the right column is where the other division responds. For a new message, you start a new row. The file lives on a network drive.
Not OP, but if I had to hazard a guess, it started as a rudimentary issue tracker and grew into a formalized system over time, maybe? I've worked with many a project manager who "knew Excel" and liked to use it for things it should never be used for, and sometimes PMs get promoted and take their dumb little systems up the org chart with them.
Bypassing communication archiving requirements? Years ago, I worked for a company that logged all IM, etc, that occurred in a companies intranet. There were laws that required all communications to be preserved for certain industries.
This sounds like a workaround to avoid chat history
I used to see this a lot when a team had to engage with an external vendor temporarily (or not so temporarily), but the only approved software both companies shared was Office before Teams was ubiquitous.
In the worst case, the file wasn't able to be shared live (e.g., SharePoint), so it was just going back and forth in email attachments. That was just as much of a nightmare as you'd guess.
So they were sending emails with a file attachment containing... messages? =_= How about using the emails themselves to, you know... type the message?
Let's not pretend like Teams is much better, though (especially the macos client). Just another inexplicably ugly purple monolith with native search worse than Excel's. At least if it were a telephone I could change the ringer/notification sound. Even if it were a couple of polystyrene cups with twine pulled taut between them, I could use a soothing green magic marker on my cup.