"Gee, that river's running uphill. Is it magic? If it is, what's the cause?"
"Gee, there aint many people around. How do they communicate? Is it magic? If it is, how is it done?"
Folks, we are a social people. We need company. If the humans of Eberron don't need that much company, then they really aint human.
We need contact with others. Both those within the community, and those outside the community. Without that contact we get strange. We are so used to having ready contact with literally millions of people we have no real idea what true isolation is like. The closest anybody comes in American society is someone kept in isolated confinement, and even then he has occasional contact with somebody else.
My sin is that I'm asking people to think about things they'd much rather not think about. I'm pointing out the Emperor's cheap banana hammock, when he should be wearing a pricey one. (He's the Emperor after all, he should care about his (minimalist) clothing.

)
Why does it matter? Because it bugs our sense of rightness. It flies in the face of our knowledge of ourselves. An innate, nigh instinctual sense of what makes a human a human. Not something you learn in school or through experience, but something about us that makes us human. Something that we can't really explain, but which we notice when it is wrong or missing.
We are social animals. We like to live in relatively closs proximity to others. Any setting that does not acknowledge that has problems, and this includes Eberron.