Language is a slippery thing. What we were taught in school was a standardized, formal version of English agreed upon (i.e., bitterly fought over) by academics. However “correct” it may be considered, it probably doesn’t reflect how you’d talk to a good friend while hanging out in a coffeehouse — or the way you need to talk to your customers.
For one thing, people come from different cultural backgrounds. Where your parents were born, what they did for a living while you were growing up, the era when you were a teenager, the place you went to school, and the faith or life stance of your family (whether you accepted or rejected it) have all probably influenced the ways you speak, write and even think today.
For example, when my father didn’t catch something in a conversation, he would say, “Please?” This meant: “Would you please repeat that?”, but it was also a tipoff to whom he was speaking that his family came from Germany. Although he never learned to speak German, he was essentially saying, “Bitte?” the same way his ancestors did.
This is just one of the ways language splinters and takes on variations. It can also be impacted by slang (“ain’t” is in the dictionary now, thank you very much1), the jargon of your profession (“Get down here, stat!”), words that get shortened (delish), mash-ups (chatbot), imports from other languages (déjà vu), brand names that become common words (Band-Aid), popular culture (GOAT), and more.
What all this diversity means to a marketing writer is that it’s not enough to know “the rules”. As a writer, I need to know which set of “rules” my target audience is playing by. If the way they use language breaks the formal rules I learned in school, my copy needs to deviate in the same way.