Well, look at it from an energy cost standpoint:<p>Going to class 3x per year: extremely low cost.  Lost of free time.  2.6 GPA.
Going to class every day: extremely high cost.  Little free time.  3.x GPA (typically).<p>Given that semesters typically take 100+ days, you're talking a 30x increase in time spent to get a <i>single point GPA improvement</i>.  Lame.  This shows a problem with the classes and the teacher, as the teacher is apparently useless, not the student who is clearly smart enough to nearly BS a class and still get an easily passing grade.<p>Personally, I tend to fluctuate between 3.0 and 3.5.  I do better in a lot of classes when I don't kill my brain listening to a bad teacher, and instead just read the darned book, which they test out of anyway.  If going to the class is useless, and actively <i>harmful</i>, <i>and</i> you can get a good grade without going, what logic says you should go?<p>GPA is a laughable measurement of capability.  It's much more of a measurement of boredom / lack of social skills.  All my programming profs will (and have) happily write me a glowing recommendation, despite having a C average with one, and a low B with another.  Of course, the C average one teaches level 450+ classes, and typically fails 50% of a class or more, so a C isn't too bad anyway.