Capt O, I respect your opinion and defend your right to have them. But for me, the idea of taking a .30 caliber carbine round within 100 yards from a 10" barrel or an 18" is "same same" for me. Yes, the round was designed for rifles. My next quest is to see if I can turn it into a true "pistol" caliber with judicious choice of a pistol powder. This will at least reduce the muzzle flash.
Plus, this is America! Who said we shouldn't have fun with our guns? Hell, I like things that go BOOM and this little shooter definitely goes BOOM inside of a closed structure! I love the feel of shocks waves in the morning! Of course, only on the exterior portion of my body, nothing internally. :-) I do not think I would ask your opinion of the 7.62x51 SBR HK clones that so many seem to love. I don't get it, but I hold no grudge for the man that wants that sort of affair. All flash and bang! Sure the ballistics are dismal, but somebody is having fun. And again, I ain't calling that little monster ineffective if I am standing within 100 yards of it. It would surely kill me deader than anything else.
Would the .300 Blackout be a more efficient cartridge in the format? Sure, from what I understand about it's ballistics. But for me, also this is about generating some historical references. Like my XM177E1. Yep, the 5.56 was designed for that 18-20" barrel, but same observation, I don't want one passing through me if I am within 100 yards of the dispenser.
For me, these items just have an appeal from a historical sense. They may be crap guns to you, but for me, there are ephemeral notes from my youth.