When did Billy give his last fuck? He did not enter this world overladen with fucks, by nature of temperament, and he distributed them judiciously, but he is now out of fucks and has been for a long time.
There was a last one, there had to be. Fucks are finite, and your supply depletes until you have one left; then, none. Did Billy know that was his last fuck? If so, did he use it wisely? I hope not, because not giving a fuck about your last fuck is a wonderful way to begin not giving a fuck in general.
Mickey still has fucks; he’ll never run out. Look at him back there, giving fucks with all his might.