The Shitpic aesthetic has arisen from two separate though equally influential factors, both of which necessitate screencapping instead of direct downloading. The first is that Instagram, which has no built-in reposting function, doesn’t let users save images directly. This means that the quickest way to save an image on a phone is to screencap it, technically creating a new image. The second, more important shift is the new macro format that divorces text from image.
As a photographer it's sad to me that, in a world where we can replicate digital objects with 100% accuracy, our most popular memes are those that have degraded to almost being unrecognizable due to unintentional compression.