In serving our customers, are the customers always right. Well, it depends. If the customer is a business owner, they know the most about their business and those they serve. Or at least they should.
But when it comes to the needs their business can not generate on their own, they may seek out the services of another business that does, such as an accountant or business lawyer. It is true that many business owners have a good bit of knowledge about other areas besides their own. But it isn't to their advantage to handle areas they do not do their primary business in, because it takes them away from their business and affects their bottom line. And they may handle the other areas poorly, or not as good as another professional who does.
The tricky thing with graphic design is that everyone in the information age thinks they have the ability to design—as long as they have the right software. They may mistakenly think that graphic design is like fine art where you are just expressing yourself artistically, or it is simply useful decoration. They do not appreciate the science, craft, or history of visual communication. In the minds of some business owners this leads to an undervaluing of what a professional designer can offer their business.
Sometimes the creation of nice-looking graphics is the goal of a business, and saving money in this area appears easy to do with enough artistic skills on hand. But what is at stake is clear communication, brand clarity, and a connection with the target market on an emotional level. The best they may be able to achieve is communicating information to the target audience. But the audience will not feel any affinity towards the business, its owners, or what the business represents.
Always assess your needs and abilities, even if you've already done so in your business plan. And remember that good graphic and visual design is an investment in the future of your business endeavor that will benefit your business beyond the original intent of the design work produced.