Why does the speaker say there are great possibilities of communication breakdow

[11C] There are between 3, 000 and 6, 000 public languages in the world, and we must add approximately 6 billion private languages since each one of us necessarily has one. Considering these facts, the possibilities for breakdowns in communication seem infinite in number. However, we do communicate successfully from time to time. And we do learn to speak languages. But learning to speak languages seems to be a very mysterious process.
    For a long time, people thought that we learned a language only by imitation and association. For example, a baby touches a hot pot and starts to cry. The mother says, "Hot, hot!" And the baby, when it stops crying, imitates the mother and says, "Hot, hot! " However, Noam Chomsky, a famous expert in language, pointed out that although children do learn some words by imitation and association, they also combine words to make meaningful sentences in ways that are unique, unlearned and creative. Because young children can make sentences they have never heard before, [12C] Chomsky suggested that human infants are born with the ability to learn a language. Chomsky meant that underneath all the differences between public and private languages, there is a universal language mechanism that makes it possible for us, as infants, to learn any language in the world. This theory explains the potential that human infants have for learning language. [13A]But it does not really explain how children come to use language in particular ways.