Why most high end airguns do not have anti double feed mechanism?

You yourself can be the anti double feed mechanism. You cock it and if there's little to no resistance then you already should know you already cocked it once before so there's a pellet already loaded in that barrel so just remove that magazine before closing that bolt or lever to avoid double loading. It's just that simple. Or just buy a Taipan Veteran if you're just one of the "many dumb shooters" (your words) to remove the magazine to avoid double loading.
 
You yourself can be the anti double feed mechanism. You cock it and if there's little to no resistance then you already should know you already cocked it once before so there's a pellet already loaded in that barrel so just remove that magazine before closing that bolt or lever to avoid double loading. It's just that simple. Or just buy a Taipan Veteran if you're just one of the "many dumb shooters" (your words) to remove the magazine to avoid double loading.

Yeah this works well, if you dont feel it pulling the spring back stop cocking it before it cycles the next round. (Fx guns as an example) if you do double load and you should know you did. Just shoot them out.
 
On my FX Royals the safety will not engage if the gun is not cocked. If not cocked , probably no pellet in the chamber. If I am not sure I loaded a pellet I check my safety. Also, like someone said the cocking effort is different if the gun is already cocked and loaded. If you go too far on cocking just take the magazine out before you close the bolt. Not sure if what I said applies to other than FX Royals.
 
I agree with the OP. For Plinkers I really don’t see the benefit as their resolution to get rid of a loaded pellet is immediate most times by the methods discussed. But I’m a squirrel hunter....in the wild not at feeding stations. The squirrels I hunt have very rarely seen a human during their short life span and when they do, they will hide, sometimes for 10 to 30 minutes when hungry or for 1 hour or more when not very motivated. In a hunting scenario like this anti-double loading is very important to me, because when I see one I load the pellet and try to acquire a shot. 50% of the time a quality shot is not presented as I’m in the woods and there are many obstacles to avoid with the flight of the pellet, or if the squirrel gets alarmed and hides. So I’m sitting and waiting for another opportunity with gun cocked and ready. I love this type of hunting b/c its very challenging, and requires discipline, squirrels have VERY good Eye sight and hearing. I’m in camo from head to toe including face mask and gloves, and very still no movement. Often I will not move more than 100 yards or so and achieve a full limit, 8 in Alabama. I can always de-cock when I change locations or leave the woods, this is very safe. I could also just fire the pellet, wasting pellet and air. If I have the magazine in the breech a pellet is chambered, if not it is clear.

Beach-gunner

Dennis
 
HW100 has had it since 2004. Still waiting on the rest to catch up ;)

1593175338_5640152525ef5ed2a147ec9.44655067.jpg




The bigger thing that bugs me, is why are most guns still coming with plastic magazines like a Marauder uses? Damn I hate those things. Even RAW still uses them. They just seem like an afterthought in designing a gun. We have the gun built, now lets just toss in some kinda plastic self indexing clockwork spring powered magazine....
 
Long_Gun_Dallas

Loading...de-cocking and removing the mag, can be a very unsafe situation, as a pellet is still chambered. I hope you are aware of the often used statement..”It’s the unloaded gun that can kill you”.

Beach-gunner

Dennis

Absolutely. Always point in a safe direction #1. Always verify the gun is unloaded when you pick it up. #2 only charge/cock the gun once you are about to use it. #3 never point the gun at something you mind destroying. #4 keep your damn finger off the trigger til you are ready to fire #5

If you just follow #1, you're pretty well set, but I'm pretty excellent at following all. 

I have Colt 45 auto that I keep loaded, and cocked. One in the chamber. In the event it is needed, I won't have the time to spare to cock/load it.
 
I have been guilty of chambering a pellet while pesting but not taking the shot. I simply retract the bolt, rotate the magazine to the empty hole and de-cock the gun. Much like the old single action Colts. I personally haven’t had issues with double loading. I consider it to all fall under “gun handling” and familiarity with your weapon. Attentiveness to the task at hand is key when handling any type of projectile launchers.