A major challenge facing undergraduate teaching, and also an opportunity to greatly enhance quality at low cost to taxpayers, arises from low student study time. The public is gradually becoming aware of something that faculty have noticed for a couple of decades: most students, even at many of the more selective universities, do not study much. One recent analysis reports that in 1961, 67% of full-time students at four-year postsecondary institutions studied more than 20 hours per week. Surveys in 2003 and 2004, in contrast, reported only 20% and 13% studied more than 20 hours per week. (Babcock and Marks, 2011) Derek Bok, former president of Harvard, says the decline cannot be explained by the changing composition of students or by more students working either for pay or as volunteers. He cites a University of California survey showing that students averaged 13 hours per week studying and attending class. Most of their spare time was spent socializing, exercising, watching TV, and playing video games (Bok, 2013, chapter 9).
Just a comment here: The physics majors (or at least the ones who are succeeding) are working pretty darn hard already.
The authors then go on to blame the poor work habits on large classes, grade inflation and the use of student evaluations of teaching in evaluating faculty.