Sidewalk Passing

Today as Barry and I were walking down the sidewalk along Texas Avenue towards 6th street, we noticed a man walking in our direction. As we got nearer to each other, the man moved off of the sidewalk onto the street. (The sidewalk was large enough to handle all of us). Barry and I both nodded our heads "hello" and Barry audibly said "Howdy." The man did not return the gesture. He only gave us a little more than a glance with no facial or audible hello.

Can you guess why?