I would guess most of those people violate various of Wozniaks rules. If I look at the most popular Anki deck about medicine that's on Anki shared deck list I fully understand that learning that way isn't optimal.

That's a good point; I'm frequently frustrated by existing decks because they tend to include too much information in the answer, or not use as many cues as they could, or not repeat themselves as much, etc. A lot of people do seem to be using Anki sub-optimally, which may explain ancientcampus's observations.