I'm pretty convinced that test-first is best seen as a negotiating technique to get the time to write the tests in the first place.

"Okay, the code is done, time to write the tests" results in pressure to shorten testing, since if the golden path works then surely everything else works, right?

Your management and your sales people then say "You're a great developer, it looks like it works, and we need to deploy that code now because customers are demanding it and the competition is breathing down our necks."

It's hard to resist that pressure.

While saying that it's best practices to do TDD means you don't need to deal with that sort of negotiation.