yes, nodes have local disks, but any local filesystem the user can write to is ofen wiped between jobs as the machines are shared resources.
there is also the problem of simply distributing the image and mounting it up. you don't want to waste cluster time at the start of your job pulling down an entire image to every node, then extract the layers -- it is way faster to put a filesystem image in your home directory, then loop mount that image.
there is also the problem of simply distributing the image and mounting it up. you don't want to waste cluster time at the start of your job pulling down an entire image to every node, then extract the layers -- it is way faster to put a filesystem image in your home directory, then loop mount that image.