According to Merriam-Webster Online Dictionary a stereotype is "to believe unfairly that all people or things with a particular characteristic are the same." In daily life, stereotyping is an us vs them mentality. Race, gender, religion, education, age, nationality, employment, economics, status, abilities, disabilities—you name a difference, there's probably a stereotype to fit it. In daily life, no matter how unfair, they are often hard to escape (watch commercials), but in stories, it might not always be such a bad inequity.
I think in writing, stereotyping creates cliche characters, making shortcuts for the author, especially in secondary characters. Little thought is wasted on these minor characters. You mention a word such as 'butler' or 'blonde' or 'biker' and a perception enters the reader's mind. Another type of stereotyping I've encountered is when reading many volumes from the same author. Sometimes the same characters show up with different names, blended into author-concentric stereotype. I might be guilty of this offense, but I believe these stereotypes develop because they emerge from the same imagination. It takes work to break out of such patterns. This type of stereotyping might even appeal to some readers since they know what characters they will encounter when reading that author's material. I've also read stories where a character (main or secondary) begins as a stereotype but before the story's end, has metamorphosed into something so much more.
This said, are there genres of reading that stereotype men and women?
In romance, just look at the book covers: muscular, '6-pack' alpha males with brawny chests and huge biceps, often brunette, and with weapon in hand toting proficiency so they can be labeled 'protective.' Another stereotype is super bad boy who only need a woman's love to bring him to the straight and narrow (BS).
Women in books have been stereotyped for decades, but thankfully, some of those stereotypes are breaking down. Beware, however—new ones develop: the new powerful woman, the CEO or female elected official. Power, you know, after being considered 'chattel' for hundreds of years, goes to a woman's head only to prove the ancient adage 'women need controlling.' AND WOMEN (the largest book-buying demographic) are buying into these tomes.
Perhaps the appeal of a stereotype is that a reader can see some of the traits of a stereotype in themselves, so identify with the character.
But characters can be based on other characters. It happens in crime/suspense novels with both detectives/investigators and criminals. How many of current TV shows have a Sherlock Holmes type detective? (I'm hooked.) How many super intelligent criminals have you encountered in reading? More over, it is cross genre typing: Is Bones a reincarnation of Spock? Is Booth really Captain Kirk? Is that why I like that show so much?
Why does this happen? I believe the main reason is that a certain stereotypes sell stories, whether in print, TV or film...until they don't. Then the publishers/producers look for the next hot selling character type and publish stories with those character profiles. The reading public goes through trends often identified by generational shifts and major social crisis, and these changes can help create those stereotypical profiles. They may go out of style and disappear only to return at some future time.
For the last few years we have been going through the super intelligent 'nerd' stereotype.
And the 'bimbo' girlfriend never seems to go away, or the too smart, unattractive spinster stereotype.
How do I try to prevent stereotyping in my writing? I've used two methods.
The first is determining my characters' personality styles. The Personality Self-Prortrait (1990) by John M. Oldham, MD and Lois B. Morris, delineates personality types. Dream up a character and then decide on his or her character personality pattern. There are thirteen recognized personality styles. We all have some of the characteristics of each, but it the dominant pattern that counts. For example, do you want your character to be excessively emotional and dependent on a relationship? Someone who is vivid, spontaneous, and flirty, with an over-the-top personality? Someone who hogs attention and praise and is excessively concerned about appearance? They would have dramatic personality style and could slip into a histrionic personality disorder. The information in the book is fascinating.
The other method involves Jungian psychology delineated by archetypes, or characters with a purpose. These include heroes, mentors, threshold guardians, heralds, shapeshifters, shadows, and tricksters. While these might sound like stereotypical castings, they are not. As Joseph Campbell in The Hero with a Thousand Faces, and Valdimir Propp in his study of Russian Fairy tales, certain characteristics of plots and characters seem to have deep psychological impact and importance in the purpose of stories. While readers might not notice this, almost all story arcs display these characteristics. If you want an easy introduction, read Christopher Vogler's The Writer's Journey, Mythic Structures For Writers.
Check out the following author blogs on this topic (always fascinating reading!):