What is a primary reason for ensuring a glass is "beer clean"?

Ensuring a glass is "beer clean" is primarily important for enhancing the flavor experience of the beer. When a glass is clean, it is free from any residual oils, soaps, or contaminants that can negatively affect the beer's aroma and taste profile. Cleanliness allows the full bouquet of the beer to be experienced without interference from foreign substances that might mask or alter the intended flavors.

Additionally, a clean glass prevents issues such as foaming or excessive carbonation loss, which can detract from the overall drinking experience. While other factors like visual appeal and durability may also play a role in the enjoyment of beer, the primary focus of having a "beer clean" glass is to ensure that the flavors are presented in their best possible form.