Why is it necessary to draw a distinction between acquisition and learning?

Why is it necessary to draw a distinction between acquisition and learning?

Acquisition refers to an unconscious process that involves the naturalistic development of language proficiency through understanding language and through using language for meaningful communication. Learning, by contrast, refers to a process in which conscious rules about a language are developed often through formal instruction.
Acquisition comes about through meaningful interaction in a natural communication setting.
Speakers are not concerned with language form, but with meaning. This contrasts with the language learning situation in which students try not to make mistakes and their teacher correct them once they are found. In classroom settings, formal rules and feedback provide the basis for language instruction. According to Krashen, acquiring a language is more successful and longer lasting than learning. Learning cannot lead to acquisition.
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