Have you ever noticed this?
Kids below the age of five are usually depicted as creepily precocious brats who speak like adults and are obsessed with seeing said adults shag and get married. Okay, so they are creepy, but still, they are smart enough to master those big words and that has to count for something.
Then, they hit around ten, where they turn into sullen and emotionally needly latchkey children.
Then the teenage years are here and they become bratty rebellious twits.
Come a few years later, they become adults and star in their own stories. If they are female, they become romance heroines... which aren't exactly the pinnacle of human intelligence as we all know.
And then, they get old... and become dotty child-like brats obsessed with seeing our hero and heroine have sex. They run wild, have no sense of personal boundaries, and... well, they behave like kids below the age of five in real life (not to be confused with the Children of the Corn types in romance novels).
My conclusion? People get more stupid as they get older in romance novels.