I use Edge when using Google services such as Gmail and Chrome when using Microsoft services such as Office 365. That way they can't log me into the browser when I log into the service.
Linking your browser login to online services is incredibly invasive.
The features is no used enought, people don't know about it, and because of that, there is no pressure to improve it.
E.G: the "forget this site" button will remove all cookies, local storage, cache, etc. for one site. Very handy, because I don't want to bust my entire cache every time. But it will remove them for all containers, which sometimes is not what you need.