So I've been thinking of building a Earthship but am not enjoying the thought of pounding dirt into tires. After looking through all of Earthship literature and videos it seems that the main reason that tires are used is because it utilizes an existing resource and they can be gotten for free.

I am much more inclined to dive into a earthbag building and I am wondering if there is a structural reason for using tires rather than earthbags. I understand that you can't have the flat walls that you would if you were using tires, but other than that, is there a reason you can't build a bermed earthbag building that functions like a Earthship? (Here is the floor plan I'm thinking of)