One way to understand marketing is to call it "pre-selling".
Some people don't have to be convinced to make a purchase. A business may make/sell/offer exactly what they want - all the business has to do is open its doors to allow that money to come in.
Most people, however, need some convincing.
Ok, so, you offer food. What kind of food? Does it look good? What do other people think about your food? Are you a good chef?
Ok, so, you offer social media management. What exactly does that mean? How will you help my business, nonprofit, or city? What do other people think about the work you do?
Some of the resistance to marketing is that the time, effort, and money spent "doesn't make money". Small businesses resist marketing efforts, only reaching out to customers who are already willing to spend money because they're a safe bet. Nonprofits spend most of the year with their nose to the grindstone - only to frantically blast people with ads when it comes time to appeal for donations. Cities resist marketing because they don't understand it, assume they don't need it, and look at it as "just another thing to do".
But if they would look at marketing as pre-selling, a way to make their work easier in the future, they understanding might change. Work becomes easier because marketing has already starting the momentum moving in the direction it should go. The marketing small business creates a bigger and bigger pool of potential customers interested in and aware of what they do, the marketing nonprofit has already built an army of supporters before they ask for money, and the marketing city has invested in pride, interest, and outreach to build their community rather than just politics and infrastructure.