The most common reason I hear for not doing yoga is that "I am not flexible!" This would be like fearing to enroll for French lessons because "I don't know any French!"
There are many misconceptions about yoga. A woman came up to me after a recent talk I gave on yoga and said she had taken one yoga class in her life and had never gone back because everything happened so fast. No one explained how to do the poses and everyone was competing with each other.
I explained the other side of yoga. That Yoga was non-competitive and the use of props enabled people of all ages and levels of fitness to do the poses with correct alignment. I told her that holding the pose longer would enhance the opening or benefit. This also enabled her to find the correct alignment without being rushed. That is what changed her mind