@Loh Jane,
It is not really a part of my day-to-day life. It only becomes important because of my participation here. However, for more than twenty years in my professional life, i was a free-lance small business manager, or worked full-time as a business manager for small businesses. My experience was that the English used in business was very conservative, and that one's image with governmental agencies, with clients or potential clients and one's peers in whatever area of business one pursued was significantly affected by how well one could express one's self in writing. It was, therefore, important to me to write clearly, concisely and correctly.
Some people these days, for example, will say that double negatives don't matter, and that they are not in fact incorrect. (An example would be: "He don't make no sense.") But there is a certain large and important segment of the literate population who consider double negatives wrong. It would be foolish to ignore this. This is especially true in business relations, where people will be harshly judged for not using what that community considers proper English.