Stuff doesn't always completely break -- e.g. Google forcing new Chrome-only web standards on certain sites and making other browsers like Firefox resort to alternatives which can end up being 5x slower [0], or serving a more dated design of google search on FF mobile vs Chrome. I suspect this sort of thing might be enough to make some people switch.

And I have had a few experiences with sites not loading properly in the last few months. Try windy.com for example: on FF 90 with no extensions enabled and tracking protection on 'balanced' I get blue and yellow banding on the map, and the wind gusts graphics fail to load properly. I have reported a few of these instances in the past, but a lot of the time I'd rather just switch to chromium temporarily and continue with what I'm doing.

[0] https://www.cnet.com/tech/services-and-software/mozilla-exec...