I don't think you get it, its not about looking at the dick itself its about the act of the dick penetrating, and the bigger it is, the more visible the penetration act is, therefor it has a bigger impact on most of the audience, that's about it. Some people get caught up on some specifics though, like exactly how a vagina is shaped, or how a dick is shaped, or if its circumcised or not, or whatever, some people don't care because its the act itself that is important, just as size doesn't matter by itself, its what you do with it. You are looking at a visual game, if you realistically would watch a average joe fuck an average jane from the side in doggy you wouldn't see that much going on