It sounds as if the airlines are already getting your $300+ because you are buying tickets for your trips. If the program does not encourage you to travel more often than you otherwise would, or cause you to buy more profitable fares, how does an airline gain?
No, not really. For example, I live in Northern California. My wife decided last minute we would take our daughter to DisneyLand for her birthday. I looked up the flights and they were about $200 each roundtrip on southwest( $600+ taxes and fees). I decided to just bite the bullet and drive down instead, costing me about $120 in gas and 12hours roundtrip. There have been other times when Southwest goes on sale for like $59 one way and we have flown. Same with Las Vegas etc... Those 7500 point short haul flights seem like a good deal if they had award availability. Too bad my flights are more than 500 miles long.