Originally they are yukkuri who has became small in order to live inside human's house.
Unlike the flat floors inside houses, their body can't stand the small stones and surface outside. For that reason most house yukkuri will disappear into shaved paste as soon as they became stray. They die without any use, without anyone even realizing they are there. Really, their existence is even lower that nose wax.
By the way, the picture above is an adult house yukkuri who got thrown out together with can that she entered to drink the leftover juices.
Lets stop littering.