My chickens love to kick all the straw out of the coop on the open side. After i change their coop, they kick all the straw out, and they have no straw left in there in like two days. It's so annoying!!!
They just like to "fix" things their way. I have a 3" lip on the front of the nest boxes and that seems to help keep things where they belong. I use shavings instead of straw/hay too, but I've seen many posts like yours and what you use for nesting material doesn't seem to matter when they decide to redecorate.
ETA: Must be getting late, you were talking about the coop itself. Pretty much the same answer though except I use a length of 2x4 in front of the pop door to keep the shavings in.
The final reason why they do that is because they try to make a hole in the middle of the nest. In the wild, nests are made in a hole on the bare soil, with some straws and feathers. Put a good lip in front.
So do they require as much straw in the side of the coop that they do NOT sleep in?
I use shavings not straw and I do keep a nice layer throughout the entire coop. I don't like straw for a couple of reasons--Mites like it, sometimes chickens try eating it and that can lead to impacted crop, and it tends to matt together and get really stinky/gross when it starts to get soiled or wet. Trying to put bedding down in just part of the coop is never going to work well though (straw or shavings) because the chooks will always scratch around in it and move it around.
I'm in the process of building a second coop... ahem I mean "grow-out pen" (that's what I tell hubby it is lol)
and I learned from the first one that he made so I made the chickens door and my door 10 inches from the floor of the coop because I hate that in the first coop the bedding would always end up outside. What I did in the first coop to remedy the problem is I used a board of wood (it's like 1x6 or 1x8) as a barrier to keep the bedding where I wanted it. So I have a 6-8 inch tall barrier to hold the bedding in place. I just made it so that the chickens door and my door had no bedding near them whatsoever and all of the bedding stays where I want it now... it worked out nicely. Hope this helps.
Mine like to look for pieces of wheat in the straw, so they're constantly rearranging it. I personally like straw for that reason (among others) because it gives them something to do while they're locked in the coop (if I sleep in). I built a removable lip on the front of my coop, so I can just pull it out when I need to clean and slide the old straw right out. You can see it on my BYC page.