To Learn or Credential?

At school, students both learn and get credentials of learning.  But what if they had to choose between the two?  My students act as if they care mainly about grades, not learning.  But students who "love school" often tell themselves they are different, that credentials are just icing on their learning cake.  I learned years ago, however, that our choices tell a different story.   

As a researcher at NASA Ames Lab in the late 1980s, I found it easy to sit in on classes at nearby Stanford.  I sat in on many classes in many departments, participating often in class discussions.  I never applied for admission, or paid tuition, but no one ever complained.  One professor even wrote me a letter of recommendation based on my work for his class.   

So anyone can learn at the very best schools for free, if they are willing to forego the credential.  This free ride would probably stop if more than a few people took advantage of it.  But in fact almost no one is actually interested in just learning, without the credential. 

Even official students face similar choices.  I tell grad students to focus on writing good papers, since no one will care what grades they get, as long as they pass.  I tell my teen sons to spend less homework time meeting anal formatting rules, and more on content.  But my students and sons rarely take my advice.

In my third year as a physics undergraduate at UC Irvine (in 1979), I found that my classes went over the same concepts we had learned in the first two years, just with more elaborate math.  So I decided to play with the physics concepts instead of doing the assigned homework.  I learned enough that way to ace the exams, but my grades often suffered from rigid grading formulas.  However, I had no trouble getting strong letters of recommendation.

So am I just weird, or do too many students neglect learning, relative to credentials?

Added: James Somers is more articulate than I on such matters.