Stuff in the back of your van

Why is it that you can empty you van out,and when you go back in a few days there is as much junk in the back. I cleaned out my van a month ago,and while i was getting it ready for rego it took me a hour to clean out the back.

i noticed that too aye its more convenient then a ute even if you jump in the seat you just throw whatevers in your hands in the back and you forget about it everyday, i have 4 water bottles a box full of sh!t and jumpers as far as the eye can see and elecy tape stuffs me why hahaha