It may be that they have to work late. Car stuck Meeting and socializing with friends or go to This cause they will make it home to sleep late and make a late by than they do their own activities is done after midnight.
It may be because they have to work late at night jam sessions or to socialize with friends. This causes them to be home, it's late and sleep late as well. Because they do things on their own, he would finish after midnight.
Maybe it"s because they had to work late. Traffic, meeting, or hang out with friends. This cause make them to home late and sleeping late too. Because more than they do their own activities completed would after midnight.