Props are widely read as a concession for beginners. Their function is geometric, and understanding it explains why experienced practitioners use them deliberately.
They bring the floor closer
Many standing poses assume a hand can reach the ground while the spine stays long, which depends on limb proportions and hip mobility as much as on effort.
A block raises the floor to where the hand can meet it without the spine rounding, so the intended shape is preserved.
The pose is not being made easier; a different and usually more accurate version is being made available. Reaching the ground with a rounded back is a substitution rather than an achievement.
Straps extend reach without collapsing the shape
Poses requiring a hand to hold a foot are often compensated for by rounding the back or bending the leg, which changes what the pose does.
A strap adds length to the arm so the hold is possible while the spine and leg stay in the intended relationship.
Where the stretch is felt shifts as a result, which is the whole point rather than a side effect.
Support enables genuine release
Restorative practice depends on muscles releasing, and muscles do not release while holding the body against gravity.
Bolsters and blankets support the weight so nothing needs to be held, which is what allows a position to be maintained for several minutes.
Without support, an apparently passive pose becomes a long isometric hold, producing close to the opposite of what was intended.
Bodies are proportioned differently
Limb lengths, torso length and the shape of the hip socket vary substantially, and these differences determine which poses are geometrically available.
Some limits are structural rather than a matter of flexibility, and no amount of practice alters bone shape.
Props accommodate structural variation, which is why a teacher may offer one to a practitioner who is neither new nor inflexible. Long-limbed and short-limbed students need different arrangements for the same pose.
Where the stigma comes from
Photographic conventions show unpropped poses, so props read as a deviation from a standard that was set by images rather than by teaching.
Traditions that developed props did so as teaching tools for adapting practice to individual bodies, not as remedial equipment.
Anyone practicing with an injury, during pregnancy, or with a joint condition should ask a qualified teacher about adaptations, and consult a clinician about what to avoid.