Passage One
My mother raised me with several fixed rules. One was that a gentleman always has a clean handkerchief in his rear（后面的）pocket. I can recall being a ten-year-old on the school playground， feeling the piece of cloth directly over my bottom and wondering what it was there for. Time would tell.
Every night for most of my life, I have removed from my trousers the things I'm going to need the next day-keys, wallet, and handkerchief. After 60 years, my body weight feels wrong if I'm heading out of the house with an empty back pocket.
This rule of behavior, of course, did not apply to one's children in the late 20th century. When my three kids were growing up, they all let me know that my handkerchief was ridiculously old-fashioned. They had their arguments. If you have to be prepared every day for a cold, why not carry a little packet of tissues，which saves you from that disgusting（恶心的）business o blowing your nose in the thing and then stuffing it back in your trousers?
But a handkerchief is a lot more durable（耐用的）than tissue，creates no waste，and has a far wider variety of uses. One reason my kids saw that handkerchief so often is because of the large number of chocolate mouths and skinned knees that handkerchief wiped. Can you hold the handle of a boiling pot with a tissue? Now that I am a grandfather of five, my handkerchief again has been put to use. When friends become grandfathers for the first time, I often send them a dozen handkerchiefs as a small gift. In fact, for Father's Day last year my wife gave me several new handkerchiefs. Neither of us can count the number of times she was in tears at a movie and said quietly, "Can I borrow your handkerchief?”

Why does the writer use the underlined quotation from his wife in the last paragraph?