In many countries, much of the content you would find in the U.S. store is missing. Items such as TV Shows, Books/Audiobooks and others never come. Why should you be denied access to what everyone else has?
In some countries, the latest Movies, Apps, Games and even Music come late. Why sit around waiting while others get to have all the fun first?
In most countries, Music, Movies, Apps, Games and more are much cheaper in the U.S. store after the exchange rate. Why pay more for the same?