There's a strange economics to consider with mileage programs. Each mile has a value, which depends on how you use it and what you redeem it for. If you can get a cheap enough fare and earn enough miles, you are effectively flying for free or at a deep discount when you redeem them. Plus, once you hit elite status with your airline, things get even better. United for example, upgrades you to Economy Plus for free and there is no baggage fee for the first bag. If you fly a lot, this is a decent chunk of money.

Plus, speaking for myself, I enjoy traveling for the hell of it. It's fun to tell your friends that you flew to Chicago for a pizza and came back that evening. Or even better, to New York for the weekend or a week in Italy. There are dirt cheap fares to be had and life is too short to put travel off, in my opinion. The more miles I earn in the process of traveling, the more I can travel and travel with upgrades to boot.

Whether it's worth it to you will depend on your travel patterns. But yes, this is how we do.