The unshodrunners' style causes moreflex in thefoot's springlike arch ankleandknee and engages morefootand calf muscles bluntingtheimpact on the body and making for a morecomfortable "ride."
For things that clearly do have the springlike quality of shifting irreversibly if pulled (or pushed) too far, like the collapse of ice sheets or the melting of permafrost, a boundary system that seeks to stop you getting too close to the threshold seems as sensible as a safety rail is on a parapet.