I discovered this when one of the plastic conduits came loose inside my dishwasher in precisely the right way as to spray water directly at the inside bottom of the door. The top and sides have a rubber seal, but the bottom is protected pretty much entirely by the interior shape of the door and the bottom tray.

It makes sense, if you think about it, since you would absolutely want some way for the humidity to gradually equalize if you left it alone with the door closed for a while.