Why would a funder mandate the use of an existing evidence-based practice?

Think of yourself as an administrator of a nonprofit and respond to the following prompts:
Why would a funder mandate the use of an existing evidence-based practice?
Identify possible ethical dilemmas that may arise when trying to decide whether to choose an existing program or develop a new one (such as cultural considerations, cost, feasibility, adaptability, do no harm, do nothing, or do something).
How would you justify the use of an existing evidence-based intervention or the creation of a new intervention?