I dunno, I can't see it goin' away. I think there's too many people out there who were young, immature, unmotivated, etc... and never put academics as their number one priority. Fortunately for (most) of them, they mature, get their act together, and knock their grades out of the park. For some, Post-baccs and SMP's are just too costly, so retaking classes may be a cheaper option.
I know of two people who are going back and retaking classes. Both are a little older, and they have done much better in all of their classes. That work ethic that they now have probably won't go away for them anytime soon. You give them the chance, and they can probably compete with most people in their med school class.
Sorry for the extended response, I'm feeling very philosophical for some reason, and I think people deserve a second chance if they're willing to put forth the effort.