What is the reason of adding a custom tables in the ElastiCube? As I understand all the customizations and calculations should be done in the Dashboard itself, so why do we need to create custom tables?
The reason to create the table in the EC level is reducing the load on the dashboard side. All the calculations you will do on the dashboard will impact the load time on the Front-end. If you need to execute a large calculation it is better to implement and calculate it upon the ElastiCube Build. Also any SQL changes (data type change, or translations).