My wild guess is that it is because VIZ is copyrighted and it's easier to get away with fan-tranlsations, since who's to say you're not just posting a parody of the chapter?
You're altering the product so you're not sharing the actual product. Much like how you can get away with posting anime videos on youtube by inverting the video, changing the tone, or putting logos on it.
My wild guess is that it is because VIZ is copyrighted and it's easier to get away with fan-tranlsations, since who's to say your not just posting a parody of the chapter?