Design patents allow you to continue to make a product while preventing other companies from copying the design or the look of your invention. By protecting the unique appearance you can keep more of the market shart.
Additionally, many companies are known based on their designs such as Apple, or Microsoft. Apple for example files and receives design patents on the icons for the apps on the iPhone. In addition a design patent is part of your brand, and you don’t want other companies to compromise your brand. High-end fashion designers could lose millions of dollars in revenue without design protection because anyone else could create the same design aesthetic.
Designs must be new, original, ornamental, and for an article of manufacture. According to 35 U.S.C. 173 a design patent term filed on or after May 13, 2015 shall be granted for the term of fifteen years from the date of grant. Patents issued from design applications filed before May 13, 2015 shall be granted for the term of fourteen years from the date of grant.