 Why was Humphrey being pick-pocketed so much?
The weatherman was always right: Temperature, 59; humidity, 47%; occasional light showers—but of what? The pockets of Mr. Humphrey Fownes were being picked outrageously. What made it possible was Humphrey Fownes' abstraction; he was an uncommonly preoccupied individual. He was thinking about Optimum Dome Conditions (a crisp 59 degrees, a mildly dessicated 47%) when a bogus postman, who pretended to be reading a postal card, jostled him. In the ensuing contretemps they emptied his rear pants pockets, got his wristwatch and restored the contents of the handkerchief pocket. It all went off very smoothly, like a game of put and take—the sole difference being that Humphrey Fownes had no idea he was playing. It was precipitation peculiar to a dome: feather-light fragments showering harmlessly on the city from time to time. Humphrey Fownes strode through the puffs of falling glass still intrigued by a temperature that was always 59 degrees, by a humidity that was always 47%, by weather that was always Optimum. It was this rather than skill that enabled the police to maintain such a tight surveillance on him, a surveillance that went to the extent of getting his fingerprints off the postman's bag, and which photographed, X-rayed and chemically analyzed the contents of his pockets before returning them. By the time Fownes reached his front door an entire dossier complete with photographs had been prepared and was being read by two men in an orange patrol car parked down the street. Sitting behind the wheel of the orange car, he watched Humphrey Fownes approach with a distinct feeling of admiration, although it was an odd, objective kind of admiration, clinical in nature. Conformity had become more than a social force; it was a physical necessity. He came to see that genuine quirks were rare and, as time went on, due partly to his own small efforts, rarer. Lanfierre was almost proud of Humphrey Fownes. He had even contrived to engage him in conversation once, a pleasantly absurd, irrational little chat that titillated him for weeks. You've got winds in your brain, Lanfierre, breezes of fatigue, zephyrs of irrationality—" At that moment, all at once, every last window in the house slammed shut. It rocked from side to side, it pitched forward and back, it yawed and dipped and twisted, straining at the mooring of its foundation. It expressed his weariness and distaste for people who went off and got neurotic when they could be enjoying a happy, normal existence. Fownes stopped on the porch to brush the plaster of paris off his shoes.
 for Lanfierre to get to know Humphrey's personality better
 to plant information necessary to arrest him  it's a typical behavior in this city  people typically pick-pocket him because he's distracted  for Lanfierre to get to know Humphrey's personality better