The decision was driven by weak sales compared to other fountain drinks. Root beer had a smaller customer base than Coca-Cola, Diet Coke, and Sprite. McDonald's wanted to focus on higher-volume beverages that appealed to more customers.
Some fans still remember the drink and ask when McDonald's stopped selling root beer. The brand was part of the late-1980s and early-1990s fountain lineup but was dropped before the end of the decade. Today, McDonald's does not list root beer on its core U.S. menu.
For more background on the menu change, see the official McDonald's history page here.
