In a recent, long term study conducted by the US Food & Drug Administration in collaboration with the Center For Disease Control, USA, it has been found that longer breastfeeding is associated with increased consumption of food, water and vegetables, and decreased consumption of fruit juice and sugar sweetened beverages at the age of 6 years. [1]

Personally, I think it is because the mother who breastfeeds her baby longer is more likely to ensure a healthy, balanced diet for her child – so go ahead and breastfeed your child for as long as possible.
1. Pediatrics. 2014;134:S1-S2, S21-S28