You know when you see a dropdown menu with different business industries ranging from Manufacturing to Technology, you should see one distinctly for Design. I think design deserves its own category because design is distinct enough to require that.
Putting design into 'arts and entertainment' does not really work because that is too broad a category, ranging from huge movie-making sets to small arts and crafts. Putting design in 'marketing and advertising' does not work because it ignores the tremendous craftsmanship, care and intentional creation (that requires specific skills - innate and learned) that goes into design. Putting design into the 'manufacturing' category ignores the incredible variety of design that is not limited to purely physical products.
When you use the word 'designer,' so often people think you mean an interior home designer or a fashion designer. Both of these are outlets for design but design itself is fundamentally the application of art and science to creating something of value. Design can range from graphic design that you see in print magazines and book layouts to postcards and illustrations to full fledged website layouts, products, transportation and businesses. Design is how you do things and always has conscious intention behind it.
Design to me always has a strong functional component. It is not pure aesthetics alone. It is about delivering exceptional value to your audience and your customer. Design is therefore both form and function - it has both aesthetics and utility and its primary purpose is to enhance the experience of the person using it.
Design can be as wide ranging and varied as the look and feel of a website to the interior of a plane or car or a product you hold in your hands. Design directly affects the individual experience a person has. Design is all about optimizing that experience - enhancing it and delivering the best experience that you can.
When you design a product well, you've thought not only about how well it works to deliver value to the person using it, but also how well it is made. That is how it affects energy consumption, manufacturing and business operations. Design affects the way you think as an individual and as an organization - hence the term, "design thinking."
That's why I think design deserves its own category in business. : )