There's stereotype that neither prosecuters nor defense attorneys(ies?) want critical thinkers on the jury. Limits their powers of influence.
They all say no matter how many test juries (their clients sometimes actually pay for them to try out arguments on a group of people), or how much jury study they do…. it is hard to predict how a juror will act / be influenced based on demographics.
My limited experience was similar, folks were not super predictable.