Yesterday I browsed the internet and came across a post by a tai-chi teacher who taught the stuff in Hong Kong. He said he started teaching for six months and was frustrated by his students' unwillingness to put in effort. He said they just came on Sunday for an opportunity to chat with fellow students (who are their friends), and stretch their muscles, just a little bit. Any extra demand to a student (whom the teacher considered can progress quicker) would result in making the student calling for sick next Sunday, perhaps never to appear again! After six months, he decided to teach them the coveted "Golden Turtle" stance and made them sweating all over. The next Sunday, most of them claimed to still having soar muscles and gently persuade the teacher to do it slowly!
Tai-Chi, chi-kung and meditation are internal practices that a teacher can't demonstrate their "greatness" and therefore difficult to motivate a student to put in extra effort to learn. For this yoga with its difficult asanas is in a better position (the likely injury to students is another issue). In chi-related practices, everything happens inside a practitioner's body. Worse yet, for deep meditation, "seeing lights during deep meditation" might actually scare away students!
To keep his group of students, many chi-related teachers would focus on teaching the moving forms, without having first build a chi-foundation in a student's body. This is, however, not the correct approach of teaching and any moving forms without the support of chi is not chi-kung at all! So, teachers who follow the classic (and correct) way of teaching continue to complain.