Why oh why did this finish so quickly

I just loved the series. Everything was spot on. The story line, the consequences of choices people make, the acting was just superb, the cinematography so for me it was a top notch series.
Was so into it that before I knew it I was watching the last one. Was really disappointed that there were so few episodes. So went looking to see when the next series was to be ready for this avid watcher to view it, only to find that there is no second series. Why Not??? If you do like this please ask for a second series.