Shouldn’t Marines know how to maintain a personal firearm?
Every Marine is trained to employ and maintain the weapon(s) assigned to his specific billet in his unit's Table of Organization, and those weapons are issued to each Marine by his unit. Pistol qualification and issue is MOS-specific below the rank of Staff Sergeant, so making it universal would require a major change in training, procurement, distribution and custody procedures -- all with rippling opportunity costs in budgeting, logistics and training time. Even if such a sweeping change was ordered today, it couldn't happen overnight.