The government worked with experts and understands as well as anyone else's when it is safe to travel and go back to thier homes. Lifting the bans helps reduce the congestion on the roads and that he crowding in places where there was no tsunami warning and keeps people off the streets.
The government should have lifted the tsunami advisories in Japan because, well, there is no longer any threats for tsunamis. At the end of the day, how many people really pay attention to those warnings anyway? If the government cries wolf one too many times, then it can lead to real disaster.
Japan recently suffered another devastating earthquake, and yet their government lifted tsunami advisories. This is a mistake because the threat of a tsunami lingers long after an earthquake has passed. If the advisories are no longer in place, individuals could be put at risk because they think the threat has gone away.
Tsunamis are one of the most serious natural disasters that can happen in Japan. When one happens, it is devastating. It is far better to error on the side of caution and have advisories running for longer than necessary, than to have people needless die when one hits without a warning.