/u/[email protected] has a perfect explanation here.
For me personally, it's solely about the humiliation and and sub space. It's about making me feel lesser, and my dom feeling greater.
For me, it's also something coupled with chastity cages. Uncaged I'm about average size, but there is something hot about being forcibly made smaller so to speak.
Right there with you. I just wish it wasn't so hard to find decent quality porn of it.