only 24 hours to live

Ralph returns from the doctor and tells his wife that the doctor has told him he has only 24 hours to live. Given this prognosis, Ralph asks his wife for sex. Naturally, she agrees, and they make love.
About six hours later, the husband goes to his wife and says, "Honey, you know I now have only 18 hours to live. Could we please do it one more time?"
Of course, the wife agrees and they do it again.
Later, as the man gets into bed, he looks at his watch and realizes he now has only 8 hours left. He touches his wife's shoulder and asks, "Honey, please... Just one more time before I die?"
She says, "Of course, dear."
And they make love for the third time. After this session, the wife rolls over & falls asleep.
Ralph, however, worried about his impending death, tosses and turns until he's down to 4 more hours. He taps his wife, who rouses. "Honey, I have only 4 more hours. Do you think we could.....?"
At this point the wife sits up and says, "Listen Ralph, I have to get up in the morning .... You don't

Why is a person who plays the piano called a pianist but a person who drives a racecar is not called a racist?