Wickability, the ability to transport moisture away from the skin, is far more important than absorbency. Cotton and wool absorb nearly twice as much as acrylic and retain nearly 10 times more moisture. Consequently, the fiber compresses, thus reducing both the cushioning and resilience.
Different activities generate different stress points.
Sports-specific socks are targeted to cushion the foot at the pressure points caused by that particular sport. Therefore, ski socks have extra padding at the shin, while aerobic socks have dense padding at the heel, ball, and toe. Many people buy their socks too large and the excess material bunches up at the heel or toe, causing discomfort and, possibly friction blisters. The construction of the acrylic fiber gives it a resiliency that lets the sock fit the shape of the foot more comfortably.