As an instructor I see studies express hesitation around props in every class - no matter the level. Yet props are the tools through which a student can experience the full expression of a pose while reducing the risk of injury. Most yoga injuries happen because someone was pushing to far or too hard. When we try to force our bodies to do things they aren't used to doing, we create space for injuries to happen.
I have seen more than one student tweak their lower back in triangle pose because they didn't use a block under the mat hand. There is no shame in bringing the floor up to you to achieve proper alignment. Sometimes props just help us compensate for physical attributes which we can not control. For instance, I regularly use blocks under my hands in pigeon. I have grater flexibility in my back and spine than my short arms will allow for. By raising the floor up three or four inches, I am able to experience a fuller expression of pigeon in its upright form.
The same is true for a folded blanket under the hips in seated postures. This is a prop aid I rarely see students using, yet Iit can make a huge difference in the tilt of the pelvis and thus the degree of depth in a forward fold.
So, the question becomes, why don't students use props? The first answer that comes to mind is vanity or self-consciousness. They don't see other students or even the instructor using props. So the student feels awkward about using props. To solve this problem in my group classes, I prompt students to use props regardless of whether I feel every student in the room needs that prop on that pose. Take a strap for example. Most students will not pick up a strap spontaneously to deepen a seated forward fold. Yet when first prompted to pick up their strap, take one end in each hand and place the middle of the strap over the balls of the feet, every student will use the strap to deepen his or her forward fold. Some will benefit more than others by the use of the strap, but those who need it will no longer feel self-conscious about using it.
As I see it, props are one thing in yoga that everyone - even instructors - should be using. The essentials, a strap and a blanket. Blankets are to me, the most versatile of all yoga props. Based on how a blanket is folded or rolled, it can mimic a wedge, block, bolster, mat, and provide extra cushioning under knees, feet, neck, shoulders, and back. In my classes, a blanket is as important as - and sometimes more important than - a mat.
The strap is particularly useful for two classes of yogis, the inflexible, and the inexperienced. In other words, if you aren't a rubber band and haven't been doing yoga since you could breathe, you probably can benefit from a strap. Straps help you maintain poses, give you those extra few inches you need to reach your toes or open your shoulders, and relieve part of your brain to concentrate on balance rather than grip in standing postures.
Blocks, the least portable of yoga props. Yet they are the one I encourage students to grab for every detox and yin class I teach. When you're reaching, twisting, lowering, or folding, a block can help bring the floor up to you when you can't both keep the true expression of the pose and touch the floor at the same time. Foam blocks in particular can simply make a pose more steady as when placed under the hip in pigeon or under the hands in downward facing dog for someone with very tight hamstrings.
So, the next time you walk into the yoga studio, stop and grab some props. Try them out in new ways. Find out for yourself how you can individualize the use of props to enhance your personal practice.