Just because you cannot imagine what people might need to use a computer for does not give you the right to tell them how much performance they need.
Perhaps they are going to the arctic circle and have to rely on parts lying around if anything breaks!
Perhaps they work with cutting edge computer graphics and need a brand new GPU with a certain new feature or hardware chip to test out!
Perhaps they are simulating something gigantic and it is easier to test out parts of the code on a local machine with a PCIe add in card before pushing it to a supercomputer.
This is the definition of a PRO machine, people who have extraordinary requirements and need power and flexibility. Stop telling them they have "enough", you are not in the position to make that call.