Accounting and Marketing. Unless you specialize in either of these fields, you probably don't feel comfortable doing either (or maybe one and not the other). The reason being, you know your business. Accounting and marketing are like foreign languages to you.
Right-Brain vs Left Brain:
It's not that you're incompetent or dumb. It's a known fact that people tend to be either right-brained or left-brained. Look at the graphic below. Which side do you favor?
That explains a lot!
Now, that's not saying that a creative person can't be detail-oriented. People just tend to favor one side over another. For instance, a few of years ago I held a social media marketing class for a group of accountants. By the looks on their faces, I could have been speaking Klingon. And, myself, as a creative person am terrible at math. I hate it. I find it hard to focus. That's why I have a tax enrolled agent to do my taxes. I gladly outsource that!
However, if you want new customers and to stay in business, you need to understand the basics of these functions.
First, even if you outsource it or hire someone in-house, how do you know the person or company doing it is doing it right? I've heard horror stories of bookkeepers who've embezzled funds for years without the owner knowing it. There are also business owners who have been "taken" by unscrupulous marketers who overcharge them and then don't deliver results or reports of progress.
A savvy business owner has a working knowledge of how accounting and marketing work.