I have to take a bit of issue with the sarcasm here. If someone purchases a product, it's reasonable to assume that the business will provide the product promised when purchased. In the case of transportation, the schedule is an important part of your purchase, hence why prices vary depending on the schedule.

With the exception of a weather delay, ATC delay or any other delay that is out of the airline's hands, it is reasonable to expect an airline to be able to keep their schedule. For a mechanical issue, that is the airline's responsibility. They need to keep their aircraft in working order to meet their schedule. If they cannot do this and it has an effect on a customer's plans and an effect on the product they purchased, they should 100% make their opinions known to the airline, and if they feel it is necessary, asking for a partial refund is perfectly acceptable.

I would say this should be true of all industries. If a customer is not satisfied with their purchase, especially if the purchase is not what was promised to them, they should speak up. Yes, I know there is the Contract of Carriage that is designed to protect an airline from having a passenger claiming some money back in many of these situations, but that is just a legal document (that isn't 100% enforceable by the way, but that's a whole other story). Most airlines realize that they need to beware of customer satisfaction, which is why they'll usually bend the rules of the CoC and provide some reimbursement in a case like this.