Consequently, adults tend to hold life at arm's length. They do not let life happen like children do. Language is best learned in the context of life, as life is being lived. Children often get totally absorbed, totally engrossed, completely losing track of time. That, plus their total openness, is ideal for language learning purposes.
Children can just be there.
They are not expected to talk, to respond, to initiate. They are given time to let the language in. No one expects them to come out with anything profound. When they do talk, it is perfectly okay to say anything they want. That they are beginning to talk is more important than what they say.