I think it's less about the taxes and more about shipping costs, to be honest. To compete in online retail these days, you pretty much have to offer free shipping. If you're starting off in the middle of the country already, there's an upper limit to how expensive your freight can be; the entire country is, at most, 3-4 shipping zones away.
But shipping from CA to NY, for example, is absurdly expensive (or WA to FL). I recently sent out a $150 wholesale order, and the freight on that was close to $100. That's not air shipping; that's Zone 8 ground shipping. Granted, that was for some of the heaviest items in our catalogs, but even shipping some of our lightest products to the East Coast the freight can easily run to 20% of the order value or more.
And more to the point, freight is a fixed cost that you have to pay regardless of whether your company is profitable; taxes are only based on your profits. There are steps I can take as a company to reduce my tax bill (including all the way to $0), but nothing I can do to make UPS or FedEx ship a package without paying them.
