The basic problem is that most people are not masochists and will not deliberately seek out terrible films. So the films that tend to occupy lists like this are films like Pearl Harbor or Dude Where's my Car (don't even get me started on Citizen Kane, 2001 or Mulholland Dr. lol) which sure, are quite terrible films, but they are still at least competently made. They have budgets. They have actors and not just the directors mum. If Pearl Harbor is one of the worst films you have ever seen, than congratulations because you have avoided true stinkers in your life-time.
The truly terrible films, films like
if people even come across them, take one look and know to avoid unless they enjoy pain. Its the movies with some budget, that could put together a slick trailer or have named actors that you might go 'yeah I enjoyed movie X with them, this could go well' are the movies that people will actually see and hence vote for. Even if there are plenty worse out there.