My guess it's largely laziness. People love monopolies because they are convenient and maybe herd mentality.

I generally find stores in price comparison websites (just make sure you don't visit the store directly from Google's shopping tab which might give them a commission) or ebay.

Buying the other way (US to Europe) is rarely worth it unfortunately. With 19% import tax and the ridiculous international shipping charges in the US it only really makes sense for very small items.