Why do Korea hope for the reunification of north and South Korea?

There are many reasons for this.

1. Both North and South Koreans are a same people as Koreans(like East & West Germany), and they are currently the only two countries in the world that are currently divided.
2. If war breaks out again, there is a high chance that much of the infrastructure and facilities will be damaged or destroyed, thus wasting all the effort made in the past 50+ years from one of the world's poorest countries to a economic powerhouse.
3. Currently huge amounts of money and manpower are being used to patrol the border, and if united, could be greatly reduced and be used for other purposes. Also, more investors would invest in Korea as risks would be greatly reduced.
4. The South has a powerful economy, while the North has quite a lot of important minerals and natural resources, in which combined could make an impressive synergy.

However, some are not supportive
1. After unification, South Korea would have to pour in billions and trillions of dollars to aid the North. Experts predict taxes will go up very high, and it will need some 30 times the amount West Germany poured into East Germany.