Yoga blocks and yogis have a complicated relationship. Some students, and even practitioners, shy away from using blocks for a variety of common reasons.
Some people just don’t feel comfortable using them. Others see using blocks as a sign of inferiority, playing into the myth that to correctly “do” Yoga one must be flexible at all times and not require help at all (I bust more about myths in my blog, here!), but the most predominant reason of all is a simple one.
A majority of yogis just don’t know how to use yoga blocks and therefore don’t see the point of incorporating them into their practice.