All it really comes down to is that it takes time to translate, localize, and reprint even a single series of manga. I think DRMASTER is doing a pretty good job of it, honestly. Even in Japan right now, the manga is only up to volume 7, so us getting volume 6 soon here is pretty damn awesome.
Just keep in mind that even on a very active serialized manga, it takes a month just for each new CHAPTER to be released, and generally there's around 7 chapters per volume. That's a lot of waiting, even in the home country of Japan, for each new volume.
Moral of the story? Don't be so impatient! lol (also, just to note, we don't really care if anyone talks about illegal things, just don't be linking to anything even questionably legal.)