The labor market is flexible, individual talent matters, and consumer wants ultimately determine everyone's wages. A computer wizard may enjoy a high salary for the first few years out of school, only to be surpassed later in life by someone with a talent for sales. Employers clearly reward people with good cognitive skills. College curricula used to require that graduates demonstrate them. That has changed.
Some savvy employers emphasize grades in specific courses with known content.
They know that work creates value, and they want people who have proven that they are willing and able to do it by working to improve their intellects while in college. Students who study less and party more also miss the personal satisfaction that comes from mastering both a demanding body of knowledge and the method and process required to build it. The information age is characterized by rivers of cheap, unorganized data. Fishing important facts on essential topics from those rivers is easier if one knows something to begin with. So is making sense out of a life sure to be buffeted with new innovations for the next fifty years or so.