Because it doesn’t explain Obi-Wan in Star Wars and Vader in ROTJ from 1977 to 2004. If you ignore the PT then it’s completely not-obvious. At best it’s Lucas trying to fix his earlier laziness through a retcon over 20 years later.
But the PT exists and i’m not ignoring it. And doesn’t the very fact that he bothered to fix it at all hurt your “lazy” narrative?