At present, the M-16 in 5.56 NATO chambering is dominant as the individual weapon in much of the world. The trend seems to be toward even lighter individual weapons chambered for yet smaller cartridges. Considering predominant tactical dogma, this makes sense. Infantry is seldom unsupported in the field. Light machine gun, mortar, artillery, armor, and ground attack air support are available.
Engagement is typically by storm tactics utilizing overwhelming force.
Infantry is simply not expected to engage at more than a couple hundred yards, usually after the target has been softened by support weapons. The selective fire carbine, perhaps augmented by an attached grenade launcher, is well suited to this task. The typical resistance or guerrilla fighter does not have access to these heavy weapons, nor could he provide the logistical support they require. Thus, he cannot utilize this tactical dogma. Should he engage the enemy on the enemy's terms, the resistance fighter will be utterly overwhelmed rather quickly.