Where can I find hard data on students' reasons for being students?
This is an active area of inquiry in US academia, as market research for admissions departments and also as part of the larger investigation into student "success". Our dean likes to remind us that the main reason for going to college used to be "to get an education" but now it's "to get a job" (and thus we need to be more get-a-job focused). I don't actually know which study he's quoting, but an article out this month seems to support his contention.

Twenge and Donnelly have published a retrospective study of students entering college between 1971 and 2014 surveying the students' reasons for pursuing higher education. From the abstract:


  Millennials (in college 2000s–2010s) and Generation X (1980s–1990s)
  valued extrinsic reasons for going to college (“to make more money”)
  more, and anti-extrinsic reasons (“to gain a general education and
  appreciation of ideas”) less than Boomers when they were the same age
  in the 1960s–1970s.


(Twenge, J. M., &amp; Donnelly, K. (2016). Generational differences in American students’ reasons for going to college, 1971–2014: The rise of extrinsic motives. Journal Of Social Psychology, 156(6), 620-629. doi:10.1080/00224545.2016.1152214)

Other articles that may be of interest (by no means an exhaustive list):


Balloo, K., Pauli, R., &amp; Worrell, M. (2015). Undergraduates’ personal
circumstances, expectations and reasons for attending university.
Studies in Higher Education. Advance online publication. doi:10.1080/03075079.2015.1099623
Bui, K. V. T. (2002). First-generation college students at a four-year university: background characteristics, reasons for pursuing higher education, and first-year experiences. College Student Journal, 36(1). 3+.
Kennett, D. J., Reed, M. J., &amp; Lam, D. (2011). The
Importance of Directly Asking Students Their Reasons for Attending
Higher Education. Issues in Educational Research, 21(1) 65-74.
Kennett, D. J., Reed, M. J., &amp; Stuart A. S. (2013). The impact of
reasons for attending university on academic resourcefulness and
adjustment. Active Learning in Higher Education, 14(2). First
published on June 10, 2015. doi:10.1177/1469787415589626
Phinney, J. S.; Dennis, J.; Osorio, S. (2006). Reasons to attend
college among ethnically diverse college students. Cultural
Diversity and Ethnic Minority Psychology, 12(2).347-366. doi:
10.1037/1099-9809.12.2.347
Schultz, J., &amp; Higbee, J. (2007). Reasons for Attending College: The
Student Point of View. Research and Teaching in Developmental
Education, 23(2), 69-76.