Why are people such bad drivers here?

Why is San Antonio so bad at road etiquette? No one uses their blinkers and everyone gets mad that you didn't know they wanted to get over. Then they aggressively tail you because you didn't let them over and now they want to go 90 in a 60. I often wonder if it's tied to the astronomically high illiteracy rate of this city or the insane entitlement of people here.