A、Because they want to avoid using words like "old" and "aged". B、Because they know the United States is a country of old people

"I’m seventy years old," says the gray-haired lady proudly to a man.
    "Did you hear that, everyone?" says the man to the people in the room. "This lovely lady is just seventy years young! And she doesn’t look a day over fifty."
    He has been Careful not to use the word "old". In a society where youth is so admired, old age is often seen as something sad, something to fight against. Americans prefer not to say "old people". They use the expression "senior citizens" . They do not talk about "old people’s" homes, but "retirement" homes.
    In fact, the man is not so wrong. Seventy is not very old these days. People in the U.S. are living longer and longer. In 1980,12 percent of Americans were over sixty-five years old. By 2030, 21 percent will be over sixty-five. Improved medical care means that people are living longer.
    However, Americans are no longer happy to accept the gray hair, bald heads, and boring clothes of their own parents. American women spend millions of dollars a year on operations to lift their faces and make those ugly wrinkles disappear. Men are prepared to spend even more on operations to plant new hair on their bald heads. It’s worth any money to look young.