As Poser suggested, this is not Apple's doing - they would love to offer all content in all countries - hey, why wouldn't they? It's simply because of a variety of reasons they can't do this. First is copyright laws - certain books, movies, music is not licences for release in some countries. The second is national legislation - certain countries ban the sale of certain apps, music and movies that they feel might offend cultural or religious sensitivities or for political reasons. Apple abides by all local, regional and national legislation.
Some countries simply don't have App Stores, iTunes Stores. However, many Members set up iTunes accounts in other countries and you don't need a credit card to do this, only an Apple Gift card in the currency of the country that you want to set up your account in. These are very easy to purchase on the Internet and, since you only need the card number and not the physical card, the retailer will email you that number and you're good to go in a few minutes.
Here's the official Apple advice on setting up an iTunes account without a credit card....
Creating an iTunes App Store account without a credit card
Tim