My understanding of low-carb eating is that is it closer to the natural diet we evolved eating as a species... we were certainly not consuming vast amounts of refined flour and sugar on the plains of Africa.
Rather than being simply an effective fat loss diet, or a way to maintain good BG control -- both of which are commonly discussed here -- I believe it allows the body to self-regulate to its ideal healthy weight... whether you need to lose, gain or stay where you are at
Or to answer your question another way: eating carbs will not help you gain lean mass (muscle)... you may gain weight but it will be fat.