Just a random thought, but what do medical school graduates do after graduation but before residency? I heard that residency starts in June and graduation is in May?
Moving, vacationing, chilling, enjoying the freedom while it lasts. Remember that they have no idea where they'll be in June/July until March, so they have to get housing lined up and move. Many 4th years are even pretty much on vacation after Match Day, just depends on how you schedule your rotations and electives.