My employer is a prime example for this case: We use Microsoft 365 because we need Microsoft Office and use their email hosting. And then we use Teams simply because it's already included in the package anyway, even though many employees hate it, but it's hard to argue for another solution because why pay for Slack when we already have Teams "for free"? And since Teams doesn't really need to compete on functionality…
And the rest of the MS ecosystem is full of dark patterns to funnel you onto it also. Create a new meeting in Outlook - there's automatically a Teams link in it that nobody asked for. Even if it's a Zoom meeting.
Maybe your system admins just suck?