In Marketing: Yeah I mean you knew where this was going. Hero illustrations are a marketing tool. The marketing hero illustration must be a captivating introduction. A massive point needs to be made. You need to be left both understanding what is happening, and wanting to know more.
This stuff takes time and thinking. Before one lays down words, one must imagine what happens over time and in different situations with specific kinds of people. Writers are creative, but also analytical and obsessed with all this “what if-ing” — always playing out scenes and conversations in their head (often to their own annoyance).