Global releases are a good idea in theory, but there's many difficulties in doing it it just isn't feasible for anything other than the biggest games.
Namely, each area has a different language, so you'll need to have a translation of the game in at least Japanese, English, German, French, Spanish and Italian ready for launch. This just isn't feasible in practice.
Next is the fact that you have to get it through different ratings agencies, which can take a VERY long time. It also costs a lot of money to do these two things, something which devs and publishers can't afford.
Then you have the smaller things, like having PAL/NTSC differences, which have to be accounted for, and advertisements in every area around the world, and having to send in review copies...
It's just not feasible, especially for Japanese developers, like Nintendo, Squeenix, Sony etc., as the yen is too strong for it to be feasible. There's a lot of steps to be done and money to be spent in order for games to be released, it's much easier to get the revenue from the game coming from your main market for the game (Japan, America, Europe) and worry about the rest later.