Why have used "attendance" and "enrollment" but not "the attendance" and "the enrollment"?


Context:

(From Wiki. Entry: Li Xiaolin)

Li Xiaolin is a Chinese businesswoman. She is currently the CEO of China Power International Development (SEHK: 2380). She is the only daughter of former Chinese Premier Li Peng and his wife Zhu Lin.[1] She was trained as a power generation engineer at Tsinghua University. She claims to have spent time as a visiting scholar at the MIT Sloan School of Management, however MIT stated that the only record it has of attendance by a student with Li’s name was enrollment in a “non-degree short course” open to anyone who has “intellectual curiosity” and pays $7,500 for 15 days of classes.[2] Currently, she is the only female CEO of a Hong Kong Stock Exchange-listed company.[3] She is also a member of the Copenhagen Climate Council.