Blood glucose levels cannot be augmented by mobilization of muscle glycogen due to lack of:

In Glycogenolysis glucose-6-P is conveed to free glucose by enzyme glucose-6-Phosphatase (the same enzyme is used in gluconeogenesis-last step). This last step occurs only in the liver because this free glucose in the liver is used to maintain blood glucose levels. BUT this last step is not needed in muscles because directly glucose-6-P is entering glycolysis to provide energy to muscle cells for contraction. So glucose-6- Phosphatase is absent in muscles. Muscles lack the enzyme Glucose-6-phosphatase, that's why muscles cannot maintain blood glucose levels. Liver cells have this enzyme. And therefore liver can only maintain blood glucose.