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.
I'm just answering the question about why there were multiple instances. I don't think starting with a single instance is magic either. I do think starting from many and then converging accelerates the mess a bit.
I didn't say this was the fault of Slack. I was answering the question about why multiple instances might exist.
On the subject of Teams, if you want to see something worse than dozens of Slack instances merged into one, it's what happens when those are subsequently migrated to Microsoft Teams, with one team created per Slack channel. Not recommended.
Also not Microsoft's fault. The effectiveness of these tools depends highly on the implementation.
We have slack and teams. Teams is awful, it’s silo based, separate discussions in tiny areas.
Slack means silo walls break down, channels are formed and disintegrate by people with stuff to contribute in an agile way, rather than a team structure which takes years to change.
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.