What is one established reason to refuse service to a patron?

Refusing service to a patron based on the patron looking underage is an established practice for businesses, particularly in environments that serve alcohol or age-restricted products. This is because laws require establishments to ensure they serve only those of legal drinking age. Failing to comply could lead to serious legal repercussions for the business, including fines, loss of licenses, or other penalties. Age verification is a critical responsibility for staff to ensure compliance with local regulations, and any suspicion related to a patron's age necessitates a cautious approach to prevent unauthorized service.

In contrast, factors like being overly friendly, wearing sports attire, or being alone do not directly implicate legal or safety issues that would warrant refusing service. These characteristics do not have the same compliance implications as age verification, making them less valid reasons for service refusal.