Louise > Status Update

I have a question. Why is dickism so common in erotica books? I mean why insult the length of a penis especially the villains, while the hero (even though they're jerks) have bigger one's. Surely it is a turn on but authors are like 'oh the exes and previous men of the heroine had smaller dicks so she's so surprised for the hero's dick. And yet we still read this kind of things. -_-