> I have no idea why so many people think that an argument that AI works is the same thing as an argument that AI will be profitable.

The fact that it works well for expensive categories of output (like software engineering, legal strategy, etc...) makes it difficult to imagine that it won't be profitable. You could still make an argument that the investments being made today are disproportionate, or that intense competition will stifle margins, but it's creating enough value to capture plenty of money.