That may be true for people working on their own, especially in a space without enough mirrors, or with an instructor who gives them only cursory attention, but from V's description, her trainer knows what she is looking at and does appropriate corrections.

That's a lot of why I was getting fed up with group ex even before my injury. In every class the *majority* of people didn't care about their form, and no matter how many times and how many different ways I tried to guide them, they continued to pay very little attention, do the moves in enormously dangerous ways, substitute exercises they obviously learned off TV in the '80s if they didn't like the way I was teaching, and refused to *try* to do things with proper form once they'd decided that doing it wrong "hurts."

Most people just don't care.

/rant