Each chapel is dedicated to a particular saint or relic.
Believing in the benevolent power of the saints and developing a special relationship with one particular saint is still a common habit.
The retablo is then placed in a church or a shrine devoted to that particular saint.
They might want to give honour to a particular saint.
In the summer each village holds a religious festival or panigiri dedicated to a particular saint.
When his time came he prayed to the particular saint, who called up the Devil and by force or trickery got the pact back.
After the rosary the station focus on a particular saint, or a point of catechism is held.
Each brotherhood is devoted to a particular saint.
It helps them to think about Jesus or a particular saint whose story might be told in the pictures.
Not all, I think, have appreciated the point of this particular story as applied to this particular saint.