PCC (pistol cartridge carbines) have a very definite place. When it comes to urban conflict with innocents in the area they excel.
1. They pick up enough extra velocity to really take advantage of today's defensive rounds while still limiting over-penetration.
2. They are very low muzzle flash a big plus inside and after dusk.
3. Easy to suppress for not only indoors but a suppressor will keep a meth lab from blowing up with you in it. (ok...I know that one isn't a concern for most of us but you will notice my MPA 71 is set up for an HK style suppressor)
4. They tend to be a very light and compact carbine. Still not my ideal inside a home, no long gun is, but better than some alternatives. If you live in a state that allows SBR's ( like I do) all the better. (I am speaking of the newer models, not the WWII guns)
5. When they use the same ammo and magazine as your handgun it cuts way back on logistics.
6. Recoil and muzzle flash are easily handle by even the young ones in the family, weight normally isn't an issue.
7. Low to almost non-existent recoil makes follow-up shots a breeze.
8. An effective range of 250-300 yards is more than sufficient for non-military and in an urban setting it works well for them as well.
There are many reasons to own a PCC, and I haven't even mentioned the fun factor! Compared to most rifle rounds they are inexpensive to shoot, fun at the range, very accurate, and hard hitting. They will take all manner of game in an emergency. Some like the Kel_Tec can be hidden in a tennis racquet bag. That AR is rather difficult to carry incognito out in public.
One last point...I am not singling out any one individual...this is a comment that has been made hundreds of time... "It is just a pistol caliber". This is true but how many people would get up and continue aggression towards you after receiving 2 or 3 rounds of Cor Bon DPX in the chest? How many would do so after receiving 1 round of ball there? The purpose of the rifle is for long range engagement. It extends the use of the firearm past that of the handgun. A PCC does the same thing...just not quite as far. I have shot mine at 200 yards in competition and hitting my target (a plow disc) was very easy, even at 300 yards connecting is simple. Btw, as we found out, the 7.62X25 FMJ will zip through well casing even at 200 yards. It is my favorite round and when coupled with my CZ 52 in my PPSh-41 is a great do anything combo for urban settings.