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

Times must have changed. When I joined the AF in ‘82 all airmen were M-16 trained are BMT. From there I was further trained at 3 additional AF bases for M-16 and .38’s. There were a few times when the Army provided some guard duty to support our missions, but each of us were expected to maintain proficiency with firearms and provide for our own security & defense.

In 1073, was assigned to a Titan Missile wing where we convoyed reentry vehicles with security police and armed with M-16's for which we had to be qualified. Before an assignment in Thailand in the Vietnam War had to be qualified on also the 38 pistol in case of attack! In Thailand mostly relied om the Security police for protection!

I am well versed with weapons - handguns and long guns - but where would I have gotten my hands on one if attacked? We had no weapons lockers in Primary Care Clinic where I treated patients. Nor did we have them available when I was a young airman working on the flight line.
When at Grand Forks when we had the B-52's, tankers, and 150 Minuteman III's, we had the ABGD guys to protect the base. (I know the terminology is different now).

During my active duty 1958 - 1963 I was required to qualify with an M1 Carbine. During basic it was an 8 shot bolt action adjustable peep site rifle. On Okinawa in 1961 I also was made familiar with .30 fully automatic carbine and a .30 caliber tripod mounted machine gun, and the old 45 caliber "grease gun". We were at a more or less remote outpost called Ona Point on an East China sea beach and there were regular monthly drills with arms and ammo.
Later in Japan I was still made to qualify with a rifle. It was actually a Mossberg model 1944 bolt action .22 long. I was able to earn a ribbon with that without much trouble because it was identical to the Mossberg .22 long, 8 shot, bolt action, peep site rifle given to me on my 12th birthday.
All this while I was translating intercepted mainland Chinese manual Morse (20351-2). Ohh, I also had to learn to fully care for a Colt .45 semi automatic pistol I carried while on "burn detail" trucking bags full of paper "classified" waste to the incinerator.
Saw all the weapons I never wanted to see again

For the same reason the USCG or Navy don't teach it, being a rifleman is not something they do on a regular basis. Security forces, Shore patrol, boarding parties etc, sure, they regularly qualify, the CG even has snipers. (And darn good ones, their teams have been top ten in the last few Int. sniper competitions at Fort Benning). but the regular every day guy, not so much. I was an ET1 and qualified on the .45 because I sometimes had to guard prisoners, and occasionally had to transport classified materials. Oh I did also qualify on the ma deuce and MK-19 as I was secondary crew on both when they were mounted on the bridge.

I was USAF 1979-1983, 51150 (computer operator)
I was also a qualified Marksman with an M-16. I also have two step sons in the military. One is Army Infantry the other is USAF Pararescueman Jumper. I really don’t think you could say our Infantryman is more qualified in combat arms than our PJ. Actually, any enemy on a field of battle would rue the day they met either one of these terrific young men.

I served 1968 to1989. As a CE Prime Beef member all CE airmen had to be M-16 qualified. As did Red Horse airmen. I was awarded the marksmanship medal my entire career while I was in CE.

I can't disagree with your position. I think every Airman needs to be able to defend themselves. Prior to deployment, many, not all go through training dependent upon where they are heading. I had the fortune of going through the Combat Skills course through AFRC before deploying on AEF Silver. It was a decent course but definitely not enough to feel competent so I trained on my own with my local IDPA for techniques. In my old retired Airman mind, I think having the skills to defend should be core Airmen skills so we don't get the snide comments or worse yet, dead Airmen.

SSgt, the same goes for most members in the Navy. In 1962 I was instructed in loading, shooting, and clearing an M1 Garland, then never touched a rifle or pistol again during my tour. This is because as an Aviation Electrician I was generally never in contact with the enemy. Of course there are exception, but this is the case for 98% of Navy personnel. Unless your a Gunners Mate we don’t pull triggers, but we make sure the weapons are functioning. Everything I know about side arms I learned after I was discharged and now consider myself an armature. gunsmith

I read a few answers to get a feel on others thoughts. First off, I am a Marine. I served for four years as a CH-53 mechanic/Crew Chief. My job was 100% helicopter maintenance. If I was put into a grunt outfit, they’d have to bust me down to E-nothing because I was almost clueless about infantry. I got the same basic training as every other Marine, as well as training on the M-16A1 and M-1911. There were very basic infantry skills taught, which I never used. After the Marine Corps, I joined the Air Force. I worked on UH-1, HH-3, HH-53 and HH-60 series helicopters as a mechanic/Crew Chief. I received zero basic training from the Air Force. I also did not receive any technical school from the Air Force until I was in for 7-8 months. The difference between the two services as it relates to my job was minimal. A torque wrench is a torque wrench. The same goes for every other tool used on helicopters. Uniforms were slightly different once we went to camouflage. Up till then my uniforms were standard AF green and 89th AW blue. I retired from the AF wearing the exact same pattern and style work uniform I wore in the Marines. Our coveralls and flight suits were exactly the same between services. I will tell you that it was this “sameness” that helped me make a successful career. Some things confused me (and still do). Dining In/Dining Out, Airman, NCO and SNCO academies and esprit de corps are different and even having attended all three... confusing when I’m in my “Marine mode”. There were other little things that caught me up short off and on for my 25 year career. But essentially, once a mechanic, always a mechanic.
Now to the point of the question. Being qualified on a weapon, in my opinion, should be mandatory for all AF members. The training and discipline needed to score well enough to pass will enhance job performance. A shooting badge signifying marksmanship enhances the uniform and provides a common thread between everyone, regardless of rank or AFSC (MOS). Having a force of qualified riflemen can only make for a safer, stronger force. It does not make a force of infantrymen. If it ever became necessary to arm up, the trained Air Force Riflemen would be a secondary force used to supplement our primary defenders, Security Forces. Arming up every Airman just makes perfectvsense.