I learned with a Sr. Telemaster. That was a good trainer and every surface on that plane lifts. I would guess money is the main reason?? Never gave it much thought. There are a lot of other planes on the market besides what the manufactures call trainers but they will cost you more. That brings up the question, what is a trainer?? I have seen everything from sticks , Kings and Masters used. For a long time the SIG Kadet was a big item, with and without ailerons.