It has nothing to do with science, but everything to do with class; e.g., the historical difference in education levels between royalty and the local gentry, who are presumed to be better educated, and the peasants, who may have had little education or even none at all.
There's an expectation that people who speak for a living, such as TV reporters, teachers, and others or those who need to write reports as part of their jobs will be able to use their own language in a way that is grammatically correct. You seldom hear someone on a TV news show say something like, "The senate didn't do nothing today, as they was not in session."
I think you missed
@gleem's point, where he surmised that he had learned grammar so well that he didn't need to think about it. That is not to say that the instruction he received was irrelevant.