Not caring is typically American... The British royal family is responsible for an enormous amount of charitable work around the world, and this baby is a symbol of the continuation of their legacy and work. It's also symbolic of the passing of the responsibilities to a new generation, and hopefully a breath of fresh air into a family hit badly by scandals, poor behavior, and tragedy.
Americans are typically too self centered to notice, but this actually is sort of a big deal. Imagine if the Rockefeller family controlled GM, Microsoft, and Wal-Mart, and had been that influential for 20 generations. Think we'd pay attention to who might someday run the company? Well, the Brit royal family is sort of like that. They have global influence and in general only Americans are too caught up chasing pop culture to notice.
Not saying we ought to be celebrating or making a fuss about it, but going out of your way to express disdain or contempt is mostly a sign of ignorance about global events. Just sayin.