I haven't found any reliable sources as to why there is no second season, or confirmations saying that there will/will not be a second season.
Due to the fact that its been more than a decade since the anime was produced, I doubt there'll be more seasons.
If you want to continue with the story, you can buy the manga set on amazon, barnes and nobles, and a lot cheaper on retail like ebay. You can also read it online, though I can't tell you where.
