Maybe some of you guys can explain me this.
I believe it has to do with the fact that we are a Top Load society. People are just starting to learn how to operate the FL machines. Even Consumer reports says that leaving the door open is a safety issue, so people think they are doing the right thing by closing it up tight. This lends a nice warm, moist breeding area for mold.
With my TL machine, I always left the lid open when it wasn't operating. Same for the door of my FL machine now. That with the trap issue formerly mentioned, and the over use of softner, and high sudsing detergent some people get ICK!!!