Someone asked me recently why I do all this when quite a bit of this stuff gets translated in Del-Ray’s releases or, say, Wikipedia. The Wikipedia part should be self-evident, but from what I’ve seen, the English Negima! releases are pretty well done.
Then again, learning this language is pretty much one of my my hobbies, and translation can actually be fun when you like the subject.
So I guess the reason is, “just because.”