The humiliation for sure–but also the lack of control. It’s the inability to control something so integral to common society that makes incontinence horny to me. The shamelessness of shitting yourself and enjoying it, or feeling drawn to shit and the taboo of it. One of my favorite scat stories is probably “Bullshit Detail” and “Caught With His Pants Down.” Those stories were both super formative for me when I was first writing.