Orac, I think there is a sort of "poverty chic" in American language, where people affect a "homier than thou" sort of dialect. "It don't matter" or "Who-done-it" or "Ain'tcha" (for "haven't you") are sort of little attempts to be folksy. (There's a million of 'em!)
At least, that's how I use them. (See, you knew I was affected!) And that's how they sound to my ear. And let's face it, would David Gates have had a smash top-ten hit with "It doesn't matter to me"?
"The light I never knowed" is of course a cheap reach for a rhyme. It doesn't grate the ear nearly as much as "Songs she sang to me, words she brang to me..." which my college Hebrew professor said haunted him as the ghastliest cheap-reach-for-a-rhyme in the English language.