You'd be surprised how many famous pop piano players didn't just have lessons, they had advanced training.
Elton John studied at the Royal Academy of Music. Alicia Keys is classically trained. Lady Gaga had lessons from the age of 4.
Even someone like Vangelis - nominally self-taught, and not a reader or writer - had lessons when he was starting out.
There are many many examples on both sides. That you can cite many who have had a lot of classical training doesn't disprove the point that many others have had minimal training.
Right, I'd argue that the people without training are going to be way more surprising.