How does so much dirt find its way under there?

Actually had an hour to myself this afternoon, so instead of finding something relaxing I decide to get some cleaning out of the way and I clean underneath the oven....

 I know things drop, I know dust builds up, but really! How does so much dirt find its way under there? 

PS I will admit the picture makes it look like it's really not that bad, but there was so much more there!