Function modeling is considered potentially useful in various fields of engineering, including engineering design. However, a close look at practices reveals that practitioners do not use formal function modeling so much, while the concept of “function” frequently appears in many practical methods without a vigorous definition. This paper tries to understand why formal function modeling is not practically utilized in industry by analyzing usage cases of function. By observing product development activities in industry, the paper identifies three problems that prevent formal function modeling from wider applications in practices, namely, practitioners' neglect of function modeling, the lack of practically useful function reasoning, and the complexity of the methods and tools of formal function modeling that make them impractical. Finally, the paper proposes strategies to tackle these problems and illustrates some research efforts in this regard.