Why do people lump entire groups of people together?

t is easier for dumb people to generalize .

I think it's a simplistic way of catergorising people. So a simplistic way of thinking out of mental laziness. People with the opposite attitude will notice the nuances- shades in between that can be within a group and therefore not paint them all with the same brush and avoid generalising groups of people.

It's how we survived. Knowing that the habalabadoda tribe on the other side of the river wear horns on their backs and bones through their noses want to kill you and take your land, assuming anyone with that thing in that tribe is bad and you need to kill them first was truth for all of human life until April 2020. That's when owning toilet paper became the most important trait.