Hibernate One to many

Question

As per hibernate documentation:

To map a bidirectional one to many, with the one-to-many side as the owning side, you have to remove the mappedBy element and set the many to one @JoinColumn as insertable and updatable to false. This solution is not optimized and will produce some additional UPDATE statements.

@Entity  
public class Troop {  
    @OneToMany  
    @JoinColumn(name="troop_fk") //we need to duplicate the physical information  
    public Set<Soldier> getSoldiers() {  
    ...  
}  

@Entity  
public class Soldier {  
    @ManyToOne  
    @JoinColumn(name="troop_fk", insertable=false, updatable=false)  
    public Troop getTroop() {  
    ...  
}  

My questions are:

1. What is the advantage of such a setup. Why not create Manytonone side as the owning side
2. Why in this setup these two values are needed: insertable=false, updatable=false