|laziness, impatience, and hubris|
I have to agree with Mirod on this one to some extent: translating the language itself isn't that important and probably would be for the worse.
1) The English is easy, and utilizes basic gramatical constructs found in most (probably all) languages. This at least applies to your basic things like Use, If, While, etc... There's only a couple dozen key words in most languages that can be picked up quickly, and (speculation) probably the majority who has access to computers have had at least some exposure to English (/speculation).
2) More complex commands often don't even make sense in English. My strongest example is map. Hell, that one's so confusing at first you may be at an advantage by not having predefined concepts of what it should do! ;)
3) Imagine if you couldn't read/maintain code except from your own country. (I believe this is really the big important one.)
4) The character set might be an issue, but:
As for documentation, the Japanese take a mandatory 4 years or so of English, and the average person has little hope of tackling a technical manual. Moreover, programmers are generally bad with langauges, and I wouldn't want to force quite that much English on anyone.