That's not how it works.

Your bank will implement WEI API. Facebook will too, same as Gmail or Youtube. Any browser that does not support or has removed the WEI API will not be able to display or use any of those websites. It's the same with Netflix or Spotify - if you try to use it in a more privacy-centered browser, it simply does not work - because it those browsers do not support EME API (which is a DRM that was implemented few years ago, but for media). Firefox was against it, by the way. Firefox also quickly backed down and implemented it anyway once it rolled out, because "We ArE FoRcEd tO Do It", due to their already dwindling marketshare and people complaining and switching to other browsers because their shit ain't working on Firefox.

Everyone keeps saying "I will never use a browser that does support WEI!", but somehow it feels like they don't really realize that their internet will simply stop working for most of the content they consume, since there's no reason for Google or Facebook to not use this opportunity to forcefeed more ads to people.