Here's why:

* Alcoholic fermentation is the process where yeast converts sugars (like glucose) into ethanol (alcohol) and carbon dioxide. This is the process that makes bread rise and produces alcoholic beverages.

* Lactic acid fermentation is another type of fermentation, but it is mainly carried out by bacteria, not yeast. In this process, pyruvate (a product of glycolysis) is converted into lactic acid. This happens in muscle cells during strenuous exercise, and is also used in making yogurt and sauerkraut.

While some yeast species may perform other types of fermentation under specific conditions, alcoholic fermentation is their primary and most well-known metabolic pathway.