It is actually Montag's destiny, it's as if his physical genes have destined him to becoming a fireman. Every fireman, when he begins to think about it, has soot colored hair, dark eyes, and a heavy shadow of beard by the end of the day. It's as if people are stereotyped into their life long professions based on their physical appearances which is just how this society acts- everything is superficial. People do not have any real experiences, they only have simulated experiences. By simulating everything, including the illusion of happiness and contentedness no one becomes upset or depressed anymore, unless and until they find the time away from the TV walls and other distractions of life to really sit and think- then they realize how worthless their existence actually is, which is why there is such a large number of people attempting suicide. It is so large in fact that the society anticipates it to the point they have a machine and technicians to quickly fix these lapses in simulated happiness.