... mainly because Ju-on 2 boasts an outrageous FORTY minutes' worth of material literally taken straight out of the first Ju-on - and when you consider that the sequel only runs for 76 minutes, that leaves you with 36 original minutes' worth of film. Ho-hum. I found that deeply irritating - as if viewers simply wouldn't remember the same stuff! - not to mention dull, having to watch it all over again.
OK, that complaint aside, the byline for Ju-on 2 was that it was supposed to explain a lot of the unanswered questions from the first movie, which frankly, over 36 minutes, simply doesn't go far enough to making any kind of sense of the original's highly convoluted storyline.
There are, however, some really nice new horror sequences which show how good the film might have been, had it had some time to develop; and some of the questions raised by the original - some, but not all - are answered.
So in conclusion - if you loved the first original movie and want to see some further developments on the story, go for it - but just remember to keep your remote control to hand with your finger on the fast-forward button for forty minutes.