I used to say the same, but now I have to use Slack + Gmail + Meet + Google Calendar + Drive + whatever else Google has.

All of this has integrations into each other. Somehow a slack bot can show me calendar entries. Why I would even need such a broken UI/experience is unclear to me. I can't see when people usually work. Meet chats disappear once the meeting is over.

At Teams/Outlook you have a million other issues, but all things considered, I preferred it.

My general assumption when I see something that insane is

- some large enough customer had a workflow depending on that existing and it was built to sell them

- someone wanted a visible feature to justify being promoted

And in most cases, at least one of those is true.