There are 300 million people in the U.S. This type of left-brained thinking is like saying, every person that is born speaks their own language, so everyone in the U.S. needs to learn 300 million languages to communicate with each other.
Parents stop using traditional tongues, thinking it will be better for their children to grow up using a dominant language (such as Swahili in East Africa) or a global one (such as English, Mandarin or Spanish).