What reasons other than "the people in small states won't get a say", "this country was never meant to be a?

Err... well you don't seem like you're likely to be convinced, and you dismissed the only logical answer, off-hand...but the fact is, if only urban interests are considered when it comes to electing a national official, then rural areas will never have their interests represented. Montana is never going to be an urban center, for example, but their interests should be considered... take, for example, a political issue regarding ranching. People in California and New York won't place much interest on making sure ranchers are doing okay... they'd be all for heavily taxing the industry and/or removing subsidies. However, that would be to the detriment of us all, as we all depend on domestic beef to control the prices that we pay for a steak or hamburger. Same thing goes with farming. So, in the wisdom of our Founding Fathers, even if we don't agree with representing the interests of all Americans, whether rural or urban, in the long run, it's to all our benefit. It's the same idea, on a larger scale, with representative Democracy. Our nation would never vote to raise taxes on ourselves, and we wouldn't have things like the Interstate Highway system, if it were purely up to us.