Context: Use case (UC) descriptions are a prominent format for specifying functional requirements. Existing literature abounds with recommendations on how to write high-quality UC descriptions but lacks insights into (1) the real-world adoption of this format, (2) whether these recommendations correspond to actual quality, and (3) what factors influence the quality of UCs. Objectives: We aim to contribute empirical evidence about the adoption of UC descriptions in a large, globally distributed case company. Methods: We surveyed 1188 requirements of a case company that were elicited from 2020-01-01 until 2024-12-31 and detected 1192 UCs in various forms. Among these, we manually evaluated the 273 template-style descriptions against established quality guidelines. We generated descriptive statistics of the format’s adoption over the surveyed time frame. Furthermore, we used inferential statistics to determine (a) how conditions of the requirements engineering process affected the UC quality and (b) how UC quality affects subsequent software development activities. Results and Conclusions: Our descriptive results show how the adoption of UC descriptions in practice deviates from textbook recommendations. However, our inferential results suggest that only a few phenomena like solution-orientation show an actual impact in practice. These results can steer UC quality research into a more relevant direction.