No, it's because there are a lot of scientific results correlating it to all kinds of better health outcomes both for the child and the mother, also in developed countries.

Whether this benefit is worth the great burden two years of breastfeeding imposes on women is, of course, debatable, and each woman should choose and not be questioned on their decision (as people often do). But sweeping the issue under the rug by denying the proven benefits of extended breastfeeding is not helpful.