Let's use evolution as an example, simply because that's what comes to mind. I have no problem with evolution. I have no reason to fear it or to reject it or to hope or wish that it's not true. Right now, I'm sitting in a chair with the laptop in my lab. There's a dog to the right on the floor. I'm as certain of these facts as I am of any other fact. I'm using sight, touch, smell, sound, and even taste (I just licked my fingers), to conclude that my current environment is as I described. I'm confident that if any other human being with normal senses and intelligence came into this room, they would be equally certain that the environment is as I described.
Now, are the best scientific minds on this planet as certain about the evolution of man that was occurring millions of years ago as I am certain of my current environment?
Not sure how exactly you would compare the situations, but in a nutshell: yes.
Is the evidence equally compelling? I doubt it.
Why?
Given reason, we should.Why are we fellow atheists (hypothetically speaking) not more willing to acknowledge room for error?
There is no such reason when it comes to evolution. It is a biological theory, which is to say, it is proven fact for all practical purposes. It is as "uncertain" as gravity or the conservation of movement.
It is simply not a good choice of subject matter to attempt to encourage science to be humbler.
Had you tried, say, economics, ethics or sociology, now we would have a different dynamic.