I mean, they could go back to the provider of the clinical information with a unique ID and request follow-up. But people are still a) busy (clinical data may come from a hospital that has little interest in research; researchers want to publish and move on); b) extremely scared of making mistakes (to the point of delusion: wanting data/results to never change, even if its an improvement - because that implies there was something wrong in the past). Getting follow-up clinical data may also be out of scope of existing agreements.