Answer: It honestly depends on the scenario. Since this is the case, I thought up of and provided some scenarios.
Step-by-step explanation:
- Situation 1: If the professor can write the chapters and gather the data faster than anyone else in the university but still pays a student to collect the data at the library in his place, he is probably lazy. If this is the case, it is not sensible of him to do this when he is fully capable of doing it himself; it is his book after all.
- Situation 2: There's a possibility that he has a busy every day schedule that does not allow him to leisurely research data on his own. On top of being a professor for 8 hours a day (assuming he's full-time), he probably has extra curricular activities after work. Writing chapters also consumes a lot of time. If this is the case, then I suppose it is sensible for him to have a student help him with gathering data.
- Situation 3: The professor is not patient. A reasonable approach to writing his book (if he has a busy schedule) is: If he cannot research data and write chapters in the same day, he can research data in his free time for one day and start writing his chapters on the next day. But if the professor is not patient and wants his data now so that he can write his chapters, he is not sensible because he is not balanced; he is in a rush.
- Situation 4: He wants the student to learn something. If the professor asked a student to help him out, he most likely asked one of his own students. If the book the professor is writing is informative (possibly relating to what he teaches), then it is natural for him to want at least one of his students to learn. Basically killing two birds with one stone: having his student learn and gathering data for his book. I believe this is sensible.
This is all I could think of. If I seem a bit shortsighted, I apologize. Hope this helped!