A lot of people don’t see the use of pistol caliber carbines I think for the wrong reason. They think we buy them to replace rifles and they are not rifles. Just long barreled pistols.
I have 4, and MP5 clone, Beretta Storm carbine, a Marlin and a Rossi ranch hand in 44 Mag.
The Beretta is a 9mm and I can shoot it all day for pennies a round (reloads) and it’s a lot of fun.
Shooting it with a mounted Aimpoint is very good for offhand practice and as another mentioned it’s nice to have a long gun that uses the same round and magazine as your handgun.
No, it doesn’t have the power of a 223 but at 1100 FPS and 124 Gr it makes a good home defense gun.
"The difference between stupidity and genius is that genius has its limits" Albert Einstine