I observed this phenomenon myself back in the day. Each fall semester a new crop of freshmen girls would roll on to campus like a tidal wave. It was an absolute madhouse for the first couple of months because these girls didn't know their limits with alcohol, drugs or sex. They wanted as much of all three as possible, because they had this culturally ingrained expectation that that's what they should be doing. An 18 year old girl who is out of her parent's house for the first time and looking to have fun is one of the most glorious creatures on Earth. They are completely carefree and in the moment, so much so that they can be annoying, but they're still intoxicating to be around. Not to mention that they're at the peak of their physical beauty. So it's no surprise that every player on campus was gunning to slay as much freshman pussy as he possibly could each fall. And there was much slaying done.
After two years of that lifestyle, though, the girls become jaded and cynical. The alcochol, drugs, late nights and junk food take their toll. Their bodies start to wear down. They realize that there's nothing glorious about getting shitfaced, doing lines of coke in a frathouse bathroom then getting banged out on a couch or behind a bush. The ultimate hypocrites, they begin to judge the younger girls for indulging in the whorish and bacchanalian behavior which they had themselves just a year or two prior. At this point, most girls start looking around for a guy to date, and as long as they don't wait too long and didn't slut it up too bad they can usually find one, because a lot of guys start to get burned out of the scene by that point as well. But for the girls that don't, well...
A senior college party girl is basically a joke. We used to laugh at them, because they would come around like cougars, trying to seduce a pretty boy freshman guy who didn't know about their reputation. Invariably, these "SWUGs" would always end up managing to fuck a few young dudes each semester, who would then catch a lot of shit and be mocked for fucking the "old lady", who had by that point usually had well north of twenty cocks in her, and whose looks had faded drastically in 3-4 years.
In hindsight, the college party scene is actually a microcosm of the lifetime sexual market, compressed into 4 years. Freshmen women are highly prized, while seniors are regarded as used good and washed up. Freshman guys, on the other hand, come in with zero status, and have to establish themselves through frats or athletics to start getting access to prime pussy. Once you got the gravy train rolling as a guy, however, it only picked up steam. By junior and senior year you had built up status and were in your prime, surrounded by a sea of pussy.
Then you graduate and reality smacks you in the face.