carolene: I am not aware of FlyerTalk-friends taking flights only to get miles. It happens (often at the end of a 'qualification period') that you need some more miles to requalify (or attain) a certain status with your favorite(s) airlines - and those mileage runs can be worth the time and money you spend for them (they even can be fun meeting people and/or experiencing new places).

The higher status often provides (this varies from airline to airline: [*]better, faster treatment from the airline at booking, check-in, boarding time, service on board[*]better/higher luggage allowances[*]privileges in assigning better seats (e-plus with UA, emergency-seat-row, etc)[*]a seat guarantee even on overbooked flights when ordering 48/24 hours in advance[*]upgrades (complimentary ones and against miles)[*]mileag-bonus on every flight (25 to 100%)[*]black-out dates for mileage-award-tickets waived[*](free or rebated) access to airline-lounges[*]upgrades at hotels (by just presenting your airline-status-card)