Why don’t George and Hazel think about their son often?

Quite simply, George and Hazel do not think about Harrison often because they are not permitted to in their dystopian society that is so focused on complete equality. Because Harrison does not accept the societal ideas, he is imprisoned when he is fourteen and not allowed to be thought of by the citizens. The reader learns that, while Hazel is of average intelligence and therefore not a "hindrance" to the equal society, George has to wear a mental handicap radio to make his brain function at a more "average" level. In this chillingly brief story, George's radio goes off several times to direct his thoughts away from the direction they are going. One occasion in which this happens is when Harrison escapes from prison and George sees Harrison on the television and recognizes him. When he does, "The realization was blasted from his mind instantly by the sound of an automobile collision in his head." This literal inability to think of their son for extended periods of time makes the ending all the more bitter to the reader, when he or she understands that the couple will never mourn for their son. After Harrison's death, the couple quickly forgets the sight of their son being shot. George tells his wife to "forget sad things," to which she responds, "I always do."

The reason that George and Hazel cannot think about their son, Harrison Bergeron, very often is because of their mental handicaps. Vonnegut writes that Hazel has completely normal intelligence, which means that she can only think of certain things in short bursts. However, George has above average intelligence and is forced to wear a government-issued mental handicap radio that transmits loud, jarring noises every twenty seconds to interrupt his thoughts.
In Vonnegut's future America, the 211th, 212th, and 213th Amendments to the Constitution make each citizen completely equal in every way possible. Citizens with above average intelligence like George are forced to wear mental handicap radios while talented athletes and beautiful people are forced to wear cumbersome weights and ugly masks. Unfortunately, George and Hazel's son possesses above average intelligence and is physically gifted. Harrison is considered a threat to the government and is arrested. Sadly, both of his parents do not have the ability to think for prolonged periods of time, which is why they cannot think about Harrison.