I agree with you totally. I was referring a bit to dhtiling saying he puts a mat on every wooden floor. - no need.
At the end of the day, I am charging the same price for cement board or membrane. It is cheap insurance in my mind since wood moves and tile moves at different rates. Also you guys have courses and trainings for tiling, many guys here don't and there are a lot of failures because of improper installation, people see why and it is usually cement board or hardi installed wrong, so customers who research things feel more comfortable paying for the mat.