Having a brand new car, most people would think it would be silly to detail it. And to some degree, you are right, but there are reasons one should consider it. There are several reasons why you might want to detail a new car:
Protect your investment: A new car is a significant investment, and detailing it can help to protect that investment. Detailing can help to remove any contaminants that may have accumulated during the manufacturing, transportation process, and waiting on the car lot. It can also help to protect your car's finish from the elements. Stuff like Coatings or PPF (paint protection film) are great options for long-term protection.
Improve appearance: Even though a new car is, well, new, it may not be as clean and shiny as you'd like. There is a reason after getting one's own vehicle detail, they will sometimes say it "Looks Better Than New!" A detailing service can help to remove any blemishes and make your new car look its best. Some dealerships may only do "quick washes," which may include methods that could induce swirls. Since when they wash them, they maybe try to do 100 at once, depending on the lot.
Customize your car: Detailing can also be a way to personalize your new vehicle and make it your own. You can add window tint or different rims, customize floor mats, and more. Or even customize parts of the body or engine if you like.
Maintain value: Keeping your new car clean and well-maintained can help to maintain its value over time. This is especially important if you plan on selling the vehicle in the future. This can result in a higher sale price vs an un maintain vehicle.
Overall, detailing a new car can help to protect your investment, improve its appearance, customize it to your liking, and maintain its value over time.