In answer to your question, I think the best I can suggest is to point out the biases at work in how you're asking it and then suggest a different way of looking at it that explains why there are some of us who see it as difficult.
Most of us are physicalists now meaning that most agree that nature is all that is the case and that there are no super-natural phenomena. [Consciousness] ... must be explainable in physical terms.
- Many people are indeed physicalists. But who cares what most people are? Would that effect whether we are correct in our views?
- Even if everything is physically explainable or must be physically explainable (an interesting and unempirical claim), that does not mean everything is explained. Or that explaining it is simple.
We don't have the exact mechanism to hand now but surely it is just a matter of time.
- This seems like faith of the strongest sort of in a not-yet-proven conclusion.
Why is it that some feel that consciousness is not amenable to physical explanations (in due time) when all else around us seems to be?
- This seems to be asking why people do or do not share your faith.
What is it about how consciousness makes itself known to us that prevents us from seeing it as a physical phenomenon like all others?
- I don't think anything prevents people from viewing it in this way, but isn't the relevant question whether or not this is in fact the case? People can view the earth as flat, but we wouldn't consider that healthy.
I see two main features in your question that I think matter to understanding your question and why you don't see consciousness as a hard problem -- but also as to why others might.
Namely, it seems that you start with a strong faith in physicalism and second that you seem to think a question is not hard if the answer is known.
Regarding the physicalism faith, I'm reminded of the late 19th century and Newtownian physics, the hard problem that came up was the black body radiation problem / ultraviolet catastrophe. At the time, at least as far as I grasp, many people believed they were on the cusp of understanding everything -- save for a pesky problem that blackbodies should produce infinite energy. But let's just put that issue away and work within physicalism.
The second issue still seems to remain. What you've asserted above is that 1) if physicalism is true, consciousness is in principle understandable using science. AND 2) if this is so, that there is no hard problem of consciousness. But I think this argument is dubious in its second premise. Or at least has some explaining to do in terms of a definition of hard problem. (See for instance: wicked problem or What makes a math problem "difficult"?).
For instance, gene expression is still a difficult problem even if we are pretty sure that what's going is related to methylation. That's not quite the same thing as being able to control cancer.
Bryan Frances has written extensively on this sort of question and has some humorous quips about consciousness on his website.
A third point is that consciousness is not for us a physical phenomenon like all others considering that our experience of consciousness is our experience of all other phenomena (if consciousness can even be called a phenomenon for us). So that makes it hard in a somewhat similar way to the difficulties in isolating non-reactive nitrogen from air -- but with the problem that it's not clear how we can extricate it from hundreds of other distracting things that are not themselves consciousness.