Thanks for the reply, I don't mean to be discouraging! I totally believe people do this, I'm saying they shouldn't. There are other issues as well. Once production data is floating around different environments, it will be easy to lose track of. Then the first GDPR delete request comes in. Was this data synthetic? Was it real? I think Joe has a copy on his laptop, he's on vacation?
It gets messy. It also doesn't solve the main 'unsolvable' issue with production data: scale. It is difficult to test some changes locally because developers often don't have access to databases large enough that would show issues before getting to production. At a certain size, this is the #1 killer of deployments.