Why is it so easy to generalize?

Why do people generalize?
I might have asked this question earlier, I think but I see some questions or comments where people just say that all men are this, all women are that. All black people are this and all white people are that.
But why? It's not that simple, not everyone is the same.
People should understand that when they generalize they are only narrowing down the people whom they can connect with.
Please don't judge everyone in the same manner.
Why is it so easy to generalize?
Post Opinion