Credit card churning, manufactured spending, and points accumulation. These activities remind me of cryptocurrency in that there's profit to be made among those who participate, but it's also wasteful of time and energy. Here, credit card reward maximization rewards the status-seeking aspect within us. There's the thrill of getting something valuable (business class tickets and luxury hotels) for seemingly nothing.
In some sense, it's just being a savvy consumer, but I'd feel better if there were some sort of carbon tax placed on air travel.