Skeletal muscle lacks glucose-6-phosphatase and therefore stores glycogen for internal use rather than releasing glucose into the bloodstream.

Caveats

• One primary source (PMC-NIH) describes G6Pase as found 'mainly' in liver and kidney, which is slightly less absolute than the claim's 'lacks' framing, though other authoritative sources use unambiguous 'absence' language for skeletal muscle.
• The claim's single-cause 'therefore' framing is somewhat reductive; muscle glycogen retention also reflects muscle's high local ATP demand and other regulatory factors beyond just the absence of one enzyme.
• Muscle glycogen-derived glucose-6-phosphate can enter pathways other than glycolysis (e.g., pentose phosphate pathway), though it still cannot be exported as free glucose — the claim's 'internal use' phrasing is correct but could be more precise.