Sure, when there were a lot more domestic airlines bringing competition to almost every possible route, it was definitely about loyalty (which in itself also compromises the dollar component, of course).
Those were the times of the mileage runs, finding the longest possible routes a fare would allow, up faring to higher fare classes just for the extra miles, competitions to qualifying for status with the lowest possible spend, and so on. Eventually, people wanted to discuss and share strategies, which led to the creation of this forum, FlyerTalk.
Back then, airlines needed real incentives to make you fly with them. Nowadays, the lack of competition is enough of an incentive.