Actually, there are companies that try to fill the gap. They have an address in US that you can use when ordering in an US-only online shop, and they will re-mail it to you in Europe. It is not cheap and a bit complicated, but it works.
Also, if you read my comment carefully, I used the word "half" a lot. There are many online shops that have no problem with shipping to eastern Europe. I can get my stuff online, it is just much less convenient.
The problem here is really simple. People in countries that are being left out have a strong feeling that the decision many companies make, not to ship to these countries, is often not based on rational reasoning. Yes, we can use the gap as an entrepreneurial opportunity, but that is beside the point. The point here is that we want to alert the companies that reconsidering their policy may be beneficial to them as well as to us.
(Try to walk in my shoes for a moment: You find something interesting on Amazon, try to order it... bang, not shipping this there. You search for it on google, try a few other shops, and maybe the third one will ship it. Even though you succeed, you still feel... discriminated.)