College is losing its romantic lustre. Students used to believe in education for itself, but now ambitious students just cram in more classes and activities to graduate faster or pad their grad school applications. Before, a student studying the American Revolution in class might go to the library and flip through the books in the professor's "suggested reading" section on the syllabus looking for a particularly interesting book to read thoroughly. And while he was there he would see other books in the stacks and end up reading for a couple of hours. Then he'd bring up what he learned in conversations with other engaged students.
Students would feel good about studying like that. They were learning. It was making them better than they used to be. Not only that, going to college was what they were supposed to do to succeed, and studying and discussing ideas was what you were supposed to do in college, so reading books about the American Revolution, or Sartre, and talking about them with your friends was pretty closely linked with your future comfort, according to the rules of society.
Less capable students would study for three hours because it was the only way they could pass their classes. (The ones who were smart and ambitious but not academically engaged? They're busy puking with rich men's sons. They pull down the studying averages, but later they'll subsidize all that economically unproductive studying as generous alumni.)
So what happened? Three things.
First, not many people have to study that hard to pass their classes. Professors used to set challenges for students that would force them to study, like difficult papers and exams. Now, that is seen as authoritarian and sadistic. You aren't allowed to test anybody just to make them study, because many people find studying difficult, even unpleasant, so it must be intrinsically bad for you. Studying has to be justified, on a minute, case-by-case basis, by concrete future benefit. This is slightly better than the attitude in some countries, especially in Asia, where forcing kids to study hard is the point of the whole system, and subjects like history and chemistry are just handy tools for what is essentially a benevolent society-wide hazing ritual. However, it's a step back from understanding that studying, like exercise, is actually good for you in certain quantities, and colleges are providing a service in forcing you to do it.
I know that sounds weird to some people, so I'll explain it in a way that hopefully everybody can relate to. Many people pay personal trainers to help them work out. Exercise instruction is usually just a pretext. The real purpose of the personal trainer is to provide social expectations, and sometimes actual social pressure, to force the client to do something beneficial they would not do in the absence of pressure: work hard in the gym.
Sometimes the pressure is merely having an hour-long appointment. Having made the appointment, the client would feel guilty about skipping or arriving late. The trainer also serves as an expert whose judgment about the nature and intensity of the workout is more credible than the client's, so the client would feel unjustified in substituting a lower standard. The trainer also provides helpful emotional support by providing emotional energy and even the threat (which must be real) of disapproval. Of course, this must be calibrated to the client, but if the client knows there is no shame in giving up and going home, then the personal trainer has failed in their job of providing social pressure to help the client succeed.
This explains why colleges used to make kids work hard. Of course, now they can't, because college is seen as compulsory for success, and success itself is compulsory, and nothing compulsory can be unpleasant unless it's exactly the same level of unpleasantness for everybody. It's basic fairness. So professors who make students study hard are assumed to be emotionally damaged reactionary sadists, unless they're charismatic enough to convince everyone that they're actually doing it "for the keeeds."
Second, a lot of middle class students now have the sense of safety and entitlement that used to be confined to the rich kids. So they're partying and assuming that as long as they don't flunk out, their future is assured.
Third, ironically, college itself is no longer guarantees admission to an economically stable middle class. Students who are worried about their future need to do something that distinguishes them. Something documented, something they can put on a grad school or job application. Grades mean nothing. Grade inflation has made it pointless to work hard in your classes and learn the subject better than anyone else, because you'll end up with nothing to show for it. Spending time in the stacks reading about the American Revolution doesn't make any sense to kids worried about their future; it's entitled self-indulgence. To them, it's the same as drinking and puking every day, just another form of entertainment that normal, economically insecure people can't afford.
So what kind of kids would spend their time actually studying? Ones with old-fashioned, romantic ideas about college. Ones who aren't concerned about their future. Ones who believe they should improve their minds and let everything else take care of itself. Or ones who are lucky enough to inhabit a social milieu where studying is actually encouraged. Kids in software and engineering at least have open source and the "makers" social crowd to encourage them to work hard. Writers can write for their friends, maybe even try to get published. Kids in history and economics? They're stuck looking for an undergraduate project with an impressive-sounding title.