Suckling is a learned behavior, not an instinct.

The urge to have intercourse is known in the scientific world as a motivational force. So too is the desire to eat and drink water.

The vast majority of what a layman, such as yourself, refers to as 'instinct' in humans is either one of the aforementioned factors or it's a reflex (such as the flight or fight syndrome, which is also a reflex and not an instinct).

Use knowledge as your ammunition, not assumptions and hastily pondered musings.