They have started jumping on ideas.Then why don't they start jumping on ideas? You don't gain evidence by settling for the current evidence.
They aren't settling for current evidence, it's just that that is what the evidence is saying so far.
And jumping one new ideas won't make you gain evidence at all. The evidence will arrive independantly.
It's not like we will get evidence which contradicts the the constancy of light only when we begin investigating the theory behind it.