If it's not for you, it's for someone else. Everyone has different preferences, artists will work on whatever interests them. You don't have to like every kind of porn, because not everything is meant for you. Besides, many artists create multiple camera angles and alternate variations of their animations, to cover more bases (but these animations tend to be short and low in production value).
People have different fetishes and kinks, there's no point trying to understand it, because it's not something you can really understand, whatever works for you works. Best thing you can do is respect people, their kinks/preferences, and their freedom to explore them openly.
