Why, in philosophy, do we learn about logic and how to lyze arguments?

Epistemology is logic. Metaphorically it is like the "roadmap" of a person's thought logic. To know logic is to be able to follow that roadmap and to prevent your own roadmap from straying into "illogic", also called syllogistic "fallacies" of which there are 244. Only 12 syllogisms contain no fallacies. Most fallacies are so common we don't know when we are using them--unless you learn logic.