I know OpenAI watermarks their stuff. But I wish they wouldn't. It's a "false" trust.
Now it means whoever has access to uncensored/non-watermarking models can pass off their faked images as real and claim, "Look! There's no watermark, of course, it's not fake!"
Whereas, if none of the image models did watermarking, then people (should) inherently know nothing can be trusted by default.