I'm talking about situation like this.What do you expect? A new student walks in, never done martial arts before and so you show them all the forms and associated techniques and drills and then do some full contact sparring all in the first 2 hour lesson? If we don't do that we are withholding secrets?
A: This is the way that you do technique X.
B: If my opponent uses technique X on me, how should I counter it?
A: The counter for technique X is a secret. I can't teach you that.
B: ...
I can understand why a teacher may not want his students to learn how to counter the teacher's best technique X. May be some day his student will challenge him. He wants to make sure that his best technique X can still work on his students.