Part of the problem is that there's a reasonable chance three (and probably four) of the semi-finalists in both competitions will come from western Europe and UEFA have to spread the major finals across all the affiliated countries.
The sponsors and media prefer major cities such as London, Paris, Rome, Madrid etc as they know the hotels, transport links and brothels are up to scratch. The sponsors also like major cities near their headquarters. UEFA are only interested who has the most persuasive argument (or the fattest wallets). The fans of competing clubs are irrelevant as locals (and UEFA delegates) will always fill the grounds.
