Because it's not written clearly. If you see everything written in french on a website and no indication about the country of creation, how can you know immediately that it's a Belgium, or Swiss site and not a French site ? The problem is exactly the same.
And I don't care about your principles, because you can oppose it to an american person, but not to an european one because of the international convention. The solution is clear : you don't have choice and must respect the international convention because of its superiority to your national law.

