Why do you do that?

Pash   Wed Jan 17, 2007 7:36 am GMT
"English teachers routinely equate standard English with “grammar,” as if other language varieties and styles lack grammar, the systematic and rule-governed backbone of language. Nothing could be further from the truth."

Why do you NES teachers, and other NES, do that? Why do you equate grammar only with Standard English?
M56   Wed Jan 17, 2007 11:01 am GMT
Why do they do that, indeed? This teacher does not.