This. And the second reason is "We have KPI's with Microsoft about teams: they guarantee that it works in x% of the time, and they guarantee that it complies with our security guidelines". Notably the security is something that can never be beaten by any other application, be it on of off premises. No matter how brilliant it is. It can never beat Teams, because Teams is "good enough" and "free" at the same time.
On the top of my head, excel and all the features it has. There are probarbly lots of other things. But if Googl Workspace works then good for you. I just know there are tonnes of companies out there that just cant live without MS-Office
If you're the one in charge of the budget, paying $12.50/month for each employee does not make sense if you're already paying for an alternative. (Assuming Business is sufficient; Enterprise would be a lot more.)
I'm skeptical that even mighty microsoft can make anti-competitive claims go away by complaining to their favorite regulators. They were beat up by that. Can you provide more info?