Take that you know of 2 from recent memory and imagine someone unlucky enough to be in the top 10% of most broken sites experience by chance for the last 3 months. Those are the ones that comment/leave about it, but it's a game of attrition over a long enough time.
Webcompat used to be a lot more active (not sure if it's one of the things Mozilla has stopped actively engaging or not) but it was always a few big sites followed by an endless stream of "I'd never use that site, but that's precisely the kind of thing an average user wouldn't want to be troubleshooting" stuff. E.g. I remember seeing https://webcompat.com/issues/136422 and thinking "yeah, the hospitals I used to work at stopped testing in Firefox too - and the sites are already frustrating when they work as expected".
