Why is this zero based budget the best method of budgeting?

Zero based budget the best method of budgeting - Reason:

Zero-based budgeting (ZBB) is a budgeting method where all expenses of each new phase have to be justified. The zero-based budgeting process beginning at zero bases and each component is examined for its requirements and expenses within an organization.

Zero-based budgeting can help to reduce costs by preventing massive increases or reduced to expenditure for the subsequent period. But this has taken far more time than conventional cost-based budgeting. It’s a time-consuming process.  

It is also a case of actual revenue because their contributions are easier to justify than in customer services and R&D departments.