I think stereotypes are necessary insofar as they are how we couch our expectations of other people. A stereotype is effectively a generic personality that we put on someone so we can address our thoughts about them without interacting with them. The way I see it, they're social shortcuts.
But once you actually know someone, applying a stereotype to them is pointless unless you specifically want to spread an assumption to other people.
Stereotypes are nothing more than forms of "comedy" based off of certain views of race, gender, or group.They are basically things that play off of basic expectations of people's nationality. They can either be considered funny, or racist, usually depending on where you stand in the situation.
I believe stereotypes aren't necessary, BUT they are ghosts of a more basic function of your neurological processes, for instance if you see five large men dressed in hoodies walking your way in the middle of the night while you're walking home alone for whatever reason.
You're instinctively going to assume these guys are up to no good, it is a neurological function, even if you don't mentally acknowledge them glands are going to release adrenaline into your blood stream to heighten your fight or flight response, regardless of who said people are, perhaps they are just wearing hoodies because it is cold, but to you, they are bad news and your mind makes that leap based on previous experience, perhaps because you've seen shady characters around before wearing hoodies in your neighbourhood.
This is similar to how stereotyping imprints itself, if you see black people as lazy, you're not going to take each black person at face value, you're going to assume they are lazy.
Though they aren't necessary in modern society, I think they are a function of the human brain. It would be the same thing as say you released thousands of people with a distinctive facial tattoo and a stunning ability to lift heavy things, people would assume people with that tattoo on their face would be able to lift heavy things, even though hypothetically anyone could get one just like it.
Stereotypes like saying garry should call his mother "mum" and not "mom"?
Go check Garry.tv, he says he doesn't like that stereotype about him, so why not post something about it?
Stereotypes are pretty necessary.
When I'm walking the jumper, and accidently walk into the hood, it's important to keep clear of the negroids or I may get robbed.
Stereotypes are a natural human instinct. If you see a man that -looks- like what you imagine a serial killer to look like, you're gonna avoid them, and whether they are or not, it could end up saving your life.
What do you really mean Are They Necessary?
stereotypes aren't something you can turn on and off, you cant decide that they are no longer necessary and make them disappear.
However, I believe stereotypes are a lot like you said OP, something either formed through experience or otherwise. They provide a way to assess situations and be better prepared for what could happen. It would be ignorant to ignore stereotypes entirely because they do exist for a reason.
I wouldn't say they are necessary in general, I just think sometimes they have a use such as knowing to be cautious around certain groups of people. Some stereotypes are absolutely useless though.
Typically, stereotypes lead to prejudice against an entire group. It's also a sweeping generalization about an entire people where many outliers exist.
Every stereotype has a base, something caused it to exist. One day someone didn't wake up and go "All black people like watermelon!" or "All Irish people are drunks!" there was something that was apparent that made that stereotype exist. I don't believe stereotypes should be used as a basis to judge anyone, use that person's own merit compared to what a stereotype would say to judge them. The only good thing about stereotypes is the possible comedic value in the more strange ones and that they're great comedic fodder because they don't apply to everyone.