I'm still waiting for the end of X1999. T_T CLAMP is just as bad as scanlators; working on too many different projects at once & never seeing things through to the end. T_T
This is a good article telling why they had put X1999 on hiatus https://www.comipress.com/article/2006/03/07/3 Also, many of their works were published in magazines that closed/folded, like the first magazine Drug and Drop was published in, and since the publisher usually holds the story and character rights, not the mangaka/s, they usually can't publish it somewhere's else.
Too bad it's on hiatus again. I would like to see the ending.... (._. ) it's so good!