Chat app wasn't bundled with office. The base version only came with word, excel and powerpoint. MS is striving to make Teams a default Windows app. It is a default Office app today. Which means you're forced into it as an org with a need for some doc tools. It works poorly on all other OSes. It is simple to synergize between other MS tools but other synergiez magically work poorly (attach file, highlight bash syntax).
Sure, someone who isn't proficient in law _may_ miss these oversteps. Additionally, the US is heavily plagued by corp corruption (aka lobbying) and they'll always signal the OK sign. Luckily, the EU is more mature in the domain of privacy and free market where shady practices are fought early on (relatively). Rather than after it is too late and a large corp killed all competition.
The issue is not just VS Slack. There are a plethora of privacy oriented office products that have zero chance when a corp like MS exploits its OS brainwash to nullify all alternatives.
Parents will discretely roll their eyes, make a small show of telling the elder kid to behave, so that elder kid behaves and younger kid shuts up, and then they'll go back to the kitchen and try to finish eating their sandwiches before either of the kids lodges another complaint against the other, which would be the sixth one this evening.
In short: nothing to see here, just regular motions of the entrepreneurial game.