Here's why:

* Ancient Origins: Brewing beer has been practiced for thousands of years, long before the advent of modern biotechnology.

* Microbial Fermentation: The core process of brewing relies on the fermentation of sugars by yeast, a microscopic fungus. This is a classic example of using microorganisms to transform raw materials into a desired product.

* Selective Breeding: Brewers have historically used selective breeding to improve yeast strains for specific qualities like flavor and alcohol production.

* No Genetic Modification: Traditional brewing does not involve the direct manipulation of the yeast's genetic material.

Therefore, beer brewing perfectly encapsulates the core principles of classical biotechnology: utilizing living organisms for specific purposes through traditional practices like selective breeding and fermentation.