Because they don't realize how bad Zoom's bad acts could be for them. People didn't feel that cigarettes were bad for them. People don't feel like McDonald's is bad for them.
I work for a large MSP, one of our partners announced recently that effective basically immediately they are no longer supporting any zoom integrations due to the China connection.
Its possible to hate zoom without liking one of the alternatives. I know a lot of people hate zoom because they associate it without meeting burning due to this year and security issues.
Never used Teams. Skype, which I last used years ago, was certainly better as far as downloadable chat clients go. Google Meet runs circles around Zoom, and I don't have to install anything.
For me it one of the more enjoyable online meeting options and it leaves Teams, Skype, webex and what have you, far behind.