The nipple is for when you don't have direct access to place a catch pan underneath where the oil is being drained, for example several of my Caterpillar dozers have belly-pans that weigh several hundred pounds. So rather than spend half a day removing one I just have a hose attached to Fumoto with nipple that I can snake out to a drain pan. Folks with boats like the nipple Fumoto for the same reason. In the case of most vehicles getting one with a nipple just increases the distance the valve protrudes from the bottom of the oil pan. Personally I think the narrow profile of the nipple risks getting caught on something, especially while wheeling, as opposed to the Fumoto valve itself which is more stubby/blocky.

Just my $.02!