Not entirely true... If you write libraries for other developers you can use them as beta testers. Your customers have a production environment, but you don't. At least, that's what one of our vendors seems to think...

We have a test environment but it's a hot mess. All the data is made up and extremely low quality. All the things you would normally interface with are also in test, but getting other teams to coordinate testing in the test space is... a chore. We do the best we can with mock services, but without having real services or representative data some of the data pattern assumptions don't play out. Leaders value writing code and our lack of architects that span teams mean that when team architects either don't meet ahead of time, make assumptions, or don't ever agree on a design then...

We always host UAT. We also track logins. Guess how many users even show up for UAT, let alone actually click on anything.

This is why the vast majority of our testing happens in prod when our users are doing real work.

Sorry for the baby rant :)