Erotica/porn is trying to get across the FEELING of sex. the vibes, the fantasy, the emotions associated with it. You cant FEEL how tight a hole is on your dick through a picture, but you know what helps sell that sensation? Seeing a really big ass cock in a small hole. Or seeing a fucking BULGE from the cock in someone's torso.
so much of porn is about bridging the gap between an IRL act that uses all 5 senses, and media that can really only rely on sight and sound at most. Porn has to communicate SO MUCH with only 2 senses to work with, so yeah, no shit a lot of porn is full of "unrealistic" stuff.
porn is not meant to be a 1 to 1 simulation of actual sex. Even the most "tasteful", "realistic" porn is depicting a fantasy, an ideal. It's art! I wish people would just treat it as art!
The problem is that too many people have too much access to the internet.