Considering that niacin can be used if too much folate is taken, why is niacin also in B Complex Plus if it contains folate?

The amount of niacin included in B Complex Plus is not enough to interfere with methylation or the absorption of active methyl- forms of other B vitamins such as folate.  Niacin, too, is a very important nutrient as it assists in the normal functioning of the digestive system, skin, and nerves and is important for the conversion of food to energy. *