Turns out it's tradition to award a set of medals during the Olympic closing ceremony. The IOC say:
After the athletes' parade, a medals ceremony is held. The IOC, with the help of the OCOG, decides which event will have its medals ceremony during the Closing Ceremony (it is generally the marathon for the Summer Games).
In London in 2012 it was the Men's Marathon. In Beijing in 2008 it was the Men's Marathon. In Athens in 2004 it was the Men's Marathon. In Sydney in 2000 it was the Men's Marathon. In Atlanta in 1996 it was the Men's Marathon. I could continue.