Why don't all members of the Air Force have to be fully qualified to be a rifleman in case of hostile events?

It all comes to to how all the components are used in force projection Marines-lightweight multi mobile force that can change tactics as needed on the fly ( more decentralized command and more flexibility by platoon command level, i.e. do what it takes to get the job done. Navy - moderate scale national force projection with capability to independently mobilize to area of need relatively rapidly. Army- large scale force projection with much highly levels of Command and control structure heavy logistics and supply controls create a slower more highly planned deployment- the army provides overwhelming force capability. Air Force- Standoff support and force projection with immediate deployment capability. This means that the protections responsibility ( M4 carry permits) rely with other services when needed.
However I do agree that during basic, each Airmen should spend more that the one day at the range and should have to qualify to some standard. Back in my day we only spent half a day on the range shooting some beat up modified 16's ( I got marksmen award, easy since I was a hunter in my day)

I joined the USAF about 9 months before 9/11, and I remember being told during training that I was supposed to be a technical expert in my career field (as a draftsman, surveyor, and construction inspector). During my career (over 15 years, sadly not more), I saw a dramatic shift from the top down. As Army and Marine units were put into combat roles (sometimes they weren't properly trained for, ie convoy operations), it became apparent that the long term support roles needed to be filled. Thus, base buildup and maintenance were transferred to an ill equipped AF (since very few Airmen had been trained for any type of combat operations, particularly outside the wire). I only deployed 3 times, but all were in support of another service. I never had all the equipment necessary. I never had the support expected (after all, I was AF, why weren't they supporting me rather than the Army/Marines). I am a huge supporter of every military member being proficient with their assigned weapon ( preferably all weapon systems they will be deployed with). But the question comes down to this...do we need everyone to be a rifleman, or do we need some to be specialists? After all, the AF was created in part because not every rifleman could fix an airplane. Just food for thought.

When I was in the Air Force, we went to M-16 training every three years.Some of the guys got their marksmanship ribbons and the rest of us qualified on the weapon. When we deployed we had M-16's in our armory in case the base was over run with hostiles. Most of the time we did our job which was loading cargo planes. We didn't worry about engaging the enemy. We had soldiers, marines, and SF for protection. It would have taken a serious attack for us to get to use our weapons.

We handled them a lot more in the 80s, especially engineers, aerial port, combat communications and similar units. However, few of the admin, supply (except port and other forward deployers) and flightline personnel should be where they need more than familiarization in case of emergency. As others have noted, if the fight comes that far in, there are worse problems, and we're not keeping the aircraft in the air, which is the mission.

When the Air Force gets rid of its star rating for staying in a barracks then we should consider letting them near real weapons.

As a member of the Sabotage Alert Team, we were taught achieving high marks with the M-16 while stationed in Misawa Japan. This was a while ago so I don't know what goes on today.

Your experiences square very much with my own. I was active Army in the mid-1980s for 4 years and then later in 1997, I joined the California Air National Guard. We had familiarization fire once a year with the M-16 and record fire once every three. I am sure there are some things the Army doesn't do well but I was taught the skills of how to handle a weapon safel and fire it accurately. When were on the range, it was easy to tell who had been prior service Army and Marine Corps and who the Air Force guys were. Some of the Air Force guys were, it seemed, clueless as to which end of the weapon the live round would come out of.

The Air Force does have a few Special Ops units. I was assigned to one when i was in. But the average airman is not expected to be in combat.

Same reason Army does not have to have a pilots license.

The AF does teach their recruits how to load and fire an M16. At least they did when I went through. And as far as hitting a target? I a mear female hit my target 98 out of 100. I wasn't brought up around gun so I had no prior experience.