Setting aside the performance argument, strictly adhering to this rule makes a big difference in 3rd-party tools like Sentry. If you pre-format log messages, the parameters don't get captured, and (at least in my experience) it sometimes shows up as a separate event entirely.

Having written a monkeypatch for the stdlib logging library at Hipmunk (RIP) for our GDPR effort, I can say: I have a lot of thoughts about ``logging``, and few of them are good. But it's definitely better than print statements!