It seems that every time I read a review of a wonderful classic movie that has been remastered to an exceptional standard (A Star is Born, for example), it has been done by Criterion. Unfortunately, I then usually discover that it is a region-locked Bluray for the USA region only. Why aren't these wonderful movies available in the UK region? It is frustrating to know that this region-based system means that if you live in USA you get to see much better Blurays than in the rest of the world. Why?
Criterion does not own any movie. They buy the rights to the movies for a limited time and are often contractually obligated to restrict their releases to the US region. This causes problem even for the users in their home market. For example they had a wonderful release of the third man both in blu-ray and dvd. The movie is now part of the Studio Canal collection (which although good is not nearly as good) and Criterion box sets for that movie are no longer available. If you are a fan of Criterion, buy yourself an all region player and order their titles as soon as they are released or you may be out of luck.
Your perspective is unbalanced. There are many films released on BRD in Europe but not in America. Criterion has a very small output and do not dominate the USA market. Many Zone A BRDs in fact are Zone free: everything released by Warners or Twilight Time; most released by Sony and some released by Fox.