ā€‹Volleyball player is one of the few athletes who spends majority of the on-court time in flexed leg position. This can be a ready position, a squat in preparation for a jump or a dive. Muscles that extend the hip, knee and ankle, must be always healthy, strong and flexible.
Like other open skill sports, in Volleyball you never know what will happen. You may have to lunge deeper, turn shaper, jump higher. If the muscles don't have extra range of motion to accommodate, injuries are possible. (Add stress and electrolytes loss to the equation).