It is a mistake to say that the assumption fails because there is no evidence. Lack of evidence is part of the definition of an assumption. If an assumption is wrong because there is no evidence, that is the same as saying all assumptions are wrong. Obviously this cannot be true.

Can an assumption be good?

All kinds of tiny things, like when we turn on the tap, water is going to come out. Assumptions are part of our decision-making strategy. ... And they concluded that “A decision, even a bad one, is still way better than no decision at all”. “A decision, even a bad one, is still way better than no decision at all.”

What are assumptions based on?

An assumption is an unexamined belief: what we think without realizing we think it. Our inferences (also called conclusions) are often based on assumptions that we haven't thought about critically. A critical thinker, however, is attentive to these assumptions because they are sometimes incorrect or misguided.