Not "the best" per se.. Rather "good enough" and part of other tools the customers already use, while keeping them free so it becomes a matter of having to spend extra $$$ for another product.

Take Teams for example. It's a pig of an app IMO. Slow (takes almost a minute to start on my otherwise-fast M1 Mac), extremely high memory use, constant errors "Oops something went wrong + cute pic of ice cream", a mess visually and not dense enough UI. They focus all their time on adding new features rather than optimising. They also focus very strongly on the "for everyone", trying to be a jack of all trades, master of none.

Slack does a much better job at team collaboration IMO. Especially for tech users, it's fast, shows a lot in small screen space and isn't as heavy (though I really miss the IRC bridge!). But Teams comes for free with O365 and integrates fully with that ecosystem. So no hassle with integrating with your ID Provider etc, it's just plug and play. So if you'd want to have slack at work you'd have to make an unreasonably strong business case for all the extra cost and work.

Another example: Sharepoint. I doubt you could find anyone who would consider Sharepoint best at anything. Yet it's still used heavily in favour of other options, because it's again free if you're already in the MS ecosystem, and it integrates with all the other tools like OneDrive and Teams (both basically just layers on top of Sharepoint). So even if you're not using sharepoint, you're using sharepoint :P

I do agree they are the best at the VS Code niche. But usually this is not their game, they go for 'good enough'. Maybe it's because their developers dogfood VS Code so they couldn't stand it being slow :)

For example, VS Code is highly optimised and doesn't suffer the performance drawbacks that usually come with electron. They have optimised the hell out of it. However they never bothered to do the same with Teams, probably because they own that space anyway.