Like rifles, they are easy to aim, making them good weapons for those unskilled with firearms. In particular, pistol-caliber carbines have extremely low recoil and make less noise than rifle-caliber weapons, and their use of pistol rounds allows for ammo interchangeability with a handgun. The smaller size and lighter weight of a carbine makes it easier to carry and manipulate in close quarters than a full-size rifle, although the shorter barrel also limits its accuracy and effective range, while the reduced weight increases its recoil (something for smaller shooters to keep in mind, especially when considering a rifle-caliber carbine).
It depends on the tactics each person is using, but a carbine may be a good choice because of its close-quarter combat effectiveness, others may prefer a melee weapon or handgun for close quarters and a regular rifle for long distance. Either way a carbine is a better choice than an SMG or machine gun or any other fully automatic weapon. A carbine is one of the better firearms to use against zombies. They do not use ammo as fast as assault rifles which is important as many of you know. Most carbines are smaller versions of full size rifles, such as the Ruger mini-14. Some more examples of carbines are: Beretta Rx4 storm, Soviet SKS, Kel-Tec SU-16, Sig 550 commando, M1 Carbine, The Versatile M4 Platform, and Kel-Tec Sub 2000 among others.