Originally Posted by pmerk34
That's becuase 5.0's and above virtually all have had extensive professional instruction
When I was roving, I would see challenge ladder tournament players, especially in doubles foot faulting ad nauseam. However when I made my way over to their court, their feet magically stayed behind the line.
5.0, 5.5, it still happens. Even Serena foot faults. Although if you ask her she'll deny it.