Actually, MOST WILL NOT TRAIN a student on an AT-6 or Tiger Moth. Most will insist that the student get a trainer. This is for the student's sake, and the instructor's sanity.
And your point is? There is no magical formula, and EVERY student is different. While you MAY have done what you say, most students have their hands full with a trainer. Students need slow, predictable, and relatively stable planes to learn on. This is why NEARLY ALL instructors insist on using a trainer for learning.