Because you prompt the AI to generate Chad Britt who looks and sounds an awful lot like Brad Pitt, but not enough so to infringe on his likeness rights.
Doesn't mean you're wrong about likeness cases, but the Blurred Lines/Gaye ruling is far from canon at this point.
The first would get laughed out of court. The latter would be an obvious ripoff to anyone (perhaps excepting some soverign-citizen-level pedants).
Had they been even slightly reasonable, it never would have gone that far.