I don't think most guys are hearing that they are small and should be bigger - except from other guys or in their heads, but you're right that most bigger guys probably aren't hearing that the woman wishes he was smaller unless he's actually hurting her, but even then, she may just be gritting her teeth.

Bigger dicks can be nice to look at but that's not the same as wanting one inside you. And, for me, a lot of the dicks in porn are just freakish and weird looking, so not appealing.