(There is a hotspot on the picture to give you a close-up of the houses in the niche.)

It is presumed (because there are no written records from the period) that cliff dwellings served to protect this mostly-agrarian people from predators of either the two-legged or four-legged kind.  The paths up (where they exist at all) are difficult and require some athleticism.  As such, they are easy to defend and near-impossible to attack.