A) Enterprises for one, e.g Rendering of an HTML page vs MD in an AI IDE or even tokens (compounding costs for a communication doc may be billions in a year)
B) True, its a subset, nobody is arguing against it. HTML has overheads in terms of stylings. MD in essence is just a straight arrow.
If there is a communication between two points with ultimate low latency way with readability and threshold just enough to have the idea, MD passes that mark. As tokens needs to conserved