To me, one of the biggest benefits of flying enough with an airline to have status with them is how they treat you when something goes pear-shaped ("irregular operations," or "irrops," in airline jargon). If you fly even two or three times a year, it's not a question of whether this will happen. It's a question of when, and perhaps of how often.
Proactive rebooking by the airline, priority on any available seats to my destination, standby priority when there aren't any available seats, phone lines where you seldom have to wait more than a few seconds even when everyone in the northeast U.S. is trying to get on another flight - these things are priceless. (Being able to wait in a lounge if you're at the airport is nice too, but since anyone can buy a day pass to most lounges, by itself it doesn't justify spending more on a ticket than you have to.)