Answer:
Because a friendly refusal does not diminish the self-esteem of those who propose something.
Step-by-step explanation:
A friendly refusal is made in a simple and gentle way, without destroying anyone's self-esteem and showing reasons that allow this refusal to be made. This all maintains respect, understanding and well-being, both for those who proposed something and for those who refused. In this way we can say that a friendly refusal is preferable, because it does not create an uncomfortable situation.