Why do most LinkedIn profiles fetched via the Person Profile Endpoint return a placeholder profile picture?

Our Person Profile API Endpoint scrapes public LinkedIn profiles only. And if a user does not share his profile picture publicly, then the profile picture of the public LinkedIn profile would be a placeholder image. We cannot discern if an image is a placeholder picture or not because an image is an image. So we return the profile picture as it is -- be it a placeholder or an actual user's profile picture.