At the last company I worked at, Slack usage started as “shadow IT”. A team would need a better collaboration tool, but central IT was just a barrier. So the department head would agree to pay for it.

Over time, a few dozen or so Slack instances popped up.

These were eventually corralled by central IT and merged into a single enterprise instance, but this just magnified the messiness - overlap between channels/workspaces, vastly different usage habits by department, etc.

Most of this happened pre-Pandemic, at a time when collaboration tools were 2nd class citizens, and nobody cared too much about the sprawl.