Why do we not focus on grammar forms more in a Comprehensible Input-based class?  Because focusing on grammar is relatively ineffective way to learn a language.  According to studies over the last 30 years by Krashen and others, “Formal grammar instruction has a very limited impact on second-language competence.  Formal intensive, prolonged instruction that is limited to just a few aspects of grammar results, in general, in only modest gains on tests in which students are encouraged to think about form.” (Explorations in Language Acquisition and Use, 2003, p. vii)

Grammar is so amazingly complex that were we to set out to attempt to explain and teach even a few aspects of grammar we would soon become bogged down in theoretical study and forget what we were trying to say.  We would jettison communication.  Many aspects of grammar are as yet inexplicable to linguists.

Our time is better spent teaching specific aspects of grammar to facilitate communication on an as-needed basis.  This method helps with the immediate need and the learning tends to stick.

A certain percentage of the population tends to be grammar-oriented.   They understand grammatical explanations and they seem to crave a succinct, logical, sequential dissection of the parts of speech.  This amounts to only about 4% of the students in any given class.  Grammar study is boring and confusing to the rest of the students—and even for the grammarians, it does not help with fluent speech all that much.  But grammarians do not believe this.  Grammar remains a major method of teaching foreign languages because the 4%’ers tend to become language teachers.

Ernest Hemingway (who is buried on a ranch in Spain and was fascinated with Spanish language and culture) illustrates how a focus on correct grammar can actually impede fluent communication:

“He had complimented me on how I spoke Italian, and we talked together very easily.  One day I had said that Italian seemed like such an easy language to me that I could not take a great interest in it; everything was so easy to say.  “Ah yes,” the major said, “Why then, do you not take up the use of grammar?”  So we took up the use of grammar, and soon Italian was such a difficult language that I was afraid to talk to him until I had the grammar straight in my mind.”

(E. Hemingway, Men without Women, 1997 [1927], p. 46-47)