why do you think that everyone in the world of fahrenheit 451 thinks that, as beatty puts it, "nothing will ever happen to me...there are no consequences and no responsibilities"?

This is because real emotion is taken out of people's lives. People are saturated with superficial stimuli so that they simply lose the capacity to understand meaningful emotion. Everything in society is disposable (shades of Orwell's Brave new World) including people and emotion. There is nothing left with any intrinsic value so there is nothing to lose.