The following is my experience, so take it with a grain of salt.
Having a 4.0 (or even a 3.9+) is highly correlated with having helicopter parents who pushed little Jhonny/Jessica throughout HS (and now college) to attend to their studies to the detriment of everything else. They are almost always bio majors. Any EC they are engaged in is solely to make themselves look good, and they put in the bare minimum effort to include that in their resume later. They also tend to enjoy mission trips (er, medical tourism). These mission trips are subsidized by their helicopter parents. They are almost always white and upper-middle class.
They usually have been pressured into the premed path by their parents, or have chosen it in order to be impressive or prestigious. They have never taken time out for their own hobbies. They have never written a novel, nor even read one outside of that required lit class they took freshman year.
They have never had to deal with real adversity (ala parents getting divorced or major surgery followed by months of hospital stays/recovery). They tend to think that maintaining a 4.0 entitles them to entrance into the med school of their choice.
Overall, they expect things to be handed to them on a silver platter.
The most coddled people I know that fit this to a T also got into top 5s. The exception is that they usually play a classical instrument too (parent's choice). People on sdn really like to think that the med school admissions game is somehow just, or that interviewers see through these people. Nope. Medical school admissions continue to love these "medical mission trips" that end up really being a vacation to an island resort, and "hospital volunteering" which in almost all instances is fetching warm blankets.
If I were an adcom a medical mission trip (outside the country) would be a HUGE strike against them, but for any pre-meds reading this just play the game. It sucks, but fundraising for a vacation to puerto rico may make you feel ethically horrible, but probably not as horrible as if you got denied a cycle (which thankfully didn't happen to me).