The human body is invested in fascia. One big fascia bag with 600 some compartments for muscles is one term that is being thrown around. It invests in the muscle, not just covers it. Some places in the body have even thicker fascia bands. These get names and in theory have mechanical roles in our bodies.
One of the proposed mechanisms for thick fascia in the body is something called the hydraulic amplifier effect first proposed by Gracovetsky. (spinal engine theory) Essentially in simplest form, the fascia forms a cylinder that allows the muscles to push against and thus allows greater muscular contraction.
Mathematical formulas have shown that the Thoracolumbar fascia (TLF) in the lower back improves the back strength by 30% and aids in bringing the back into extension after going in flexion.
The Iliotibial band is another fascia thickening that can have the hydraulic amplifier effect with the vastus lateralis muscle. (the largest quadricep muscle). It provides significant lateral stability. Which is why keeping this large muscle loose if of critical importance.
This can actually be over recruited. If a patient or athlete presents with a larger upper vastus lateralis it most likely is being over recruited instead of the hip abductors.
Another significant thickening of fascia is the plantar fascia. Not exactly a hydraulic effect, it has it's own name, The Windlass Mechanism. It helps create the push off in the foot. (much more complex then that) Just wanted to show a significant role in the body.