A Wikipedia parece cobrir isso muito bem:
A citação específica diretamente do Mamet:
When asked how he developed his style for writing dialogue, Mamet said, "In my family, in the days prior to television, we liked to while away the evenings by making ourselves miserable, based solely on our ability to speak the language viciously. That's probably where my ability was honed."
Isso é simplesmente o estilo de Mamet. É como ele gosta de escrever diálogos.