Don't know their rationale, but back in the day it was really popular to cat a zip file onto the end of a JPEG or PNG and upload it onto 4chan, to be able to smuggle zip files where only images were supposed to be allowed. I remember back in the day seeing the "mods are asleep, post sinks" threads where people would share pictures of sinks, and I thought it was people being goofy, but later somebody told me that people were sharing zips of CP in those threads. I don't know if it's true or not, and never cared to find out.