ISP agents would come to your house to collect your bill. If someone didn't pay, the agent would flip a cell in their excel row. And that would trigger that person's internet being suspended. Sometimes they would flip the wrong person, and you had to call them, and they would fix it.
EDIT: As many people have pointed out, Excel did suppport collaborative editing at the time.
Now, "supported" does not mean it was in any way good idea, or that it resembled how collaborative editing works in things like Google sheets or O365. Conflicts, deadlocks, etc were common - it's even why I built my first Rails app - we were given excel sheet and asked to do data entry on it over network from multiple machines, I didn't trust it despite a demo of it working and built a quick and dirty webapp.
(Source: I built one of those during my school holidays but I didn't get paid and I didn't have the balls to ask for payment)