In a nutshell: Paint is important.
Paint exists primarily to protect the metal your vehicle is made of. Therefore, protecting your paint is important to prevent corrosion. As a bonus, clean cars are a whole lot more pleasant to look at and drive than dirty cars.
Most modern cars are painted in two stages. The first stage covers the bare metal and colors the vehicle. This “color coat” is relatively thin.
The second stage is a “clear coat.” This layer protects the color coat and metal body panels further. It is significantly thicker than the color coat and is the primary focus of most detailers and detailing products.
To properly care for a car’s aesthetics is to properly care for the car’s clear coat.