What if you're doing anything which doesn't involve logins — public information, advertising, etc. – where users don't otherwise trigger something like account creation / logins?

What if you're trying to get stats about people who don't convert or otherwise give you a signal that they're using the site?

I've run into sites where things like signup or checkout are blocked behind an analytics tracker (Adobe used to recommend running theirs in a synchronous navigation-blocking mode) which meant that any problem with that service was completely invisible unless they contacted you to complain.

I also remember people wondering why Firefox users stopped using their site when they shipped the release which enabled tracking protection by default.