Standard and non-standard dialects
It is a mistake to think of the ‘standard’ variety of a language as the language, with dialects relegated to substandard status. Instead, by subscribing to the definition of ‘dialect’ as a distinct variety, we are agreeing that the standard variety itself is a dialect.
While the standard variety is regarded as a model for purposes that include language teaching and the general transmission of day-to-day information, structurally there is nothing inherently superior in the make-up of a ‘standard dialect’: non-standard dialects have vocabulary, grammar, and pronunciation which are equally detailed in structure, and indeed are often imbued with pedigrees far older than those of the standard variety of the day.
A good case of pedigree is that of while, which in West Yorkshire usage today (and well into the twentieth century in usage much further south) can mean ‘until’ in such expressions as ‘wait while five o’clock’. It would be easy to dismiss this as quaint or even wrong, but its documented history goes back at least to the fourteenth century, and it was doubtless in spoken use well before then.