Perhaps it is because economic theory is about the universal causal structure of human action and marketing is about how some people persuade other people to take particular actions in particular circumstances. If so, then, it’s likely that psychology would develop more insights about marketing than economic theory.
Austrian economists have written a lot about entrepreneurship. So that might be the literature to read to investigate what insights can be drawn in economic theory about marketing. Here is a start:
And here’s an article advocating developing an Austrian economics of marketing, advertizing, and other business practices:
Also, there have been attempts to develop marketing theory along Austrian lines: