Intelligent design
Let me start by saying that I completely appreciate the amount of time and effort that goes into thinking of, prototyping, designing, playtesting and developing a game. It takes hundreds of hours of playtest sessions to refine a game and very clever people to create a great game that flows nicely, is balanced and creates the intended player experience. So when people buy a game and change its rules without second thought, they disrespect the designers' and developers' hard work, time and effort. After all, your quick and hasty rule changes are unlikely to improve a game that has gone through years of development and been tested by many, many people. Yet, I think there are reasons why you would want to change a game, and I don't think there is any disrespect to anyone by doing so in those situations.