I hope I don't come off sounding crass, snooty or outright stupid, but after watching a goodly number of series close out with weak, confusing, unsatisfying or just plain bad endings, I've arrived at the uninformed conclusion that the Japanese simply don't have that certain sense of the dramatic when it comes to bringing a story to a close with any sort of firm, definitive ending that makes watching a series worth a person's time in the first place.
There are also instances where a series intentionally ended poorly. Take Evangelion for example, I think I read somewhere that it's creator purposely ended the series the way he did (which sucked all to hell) because he wanted the viewer to draw his or her own conclusion about the story. I'm sorry, but that's crap. When I read or watch a story, I want a solid conclusion, otherwise I feel annoyed, even angry for having invested my time and money in something that didn't give me a firm sense of satisfaction at the end.
And, judging from some of the responses I've read on this post, other people feel the same way I do----CHEATED! Perhaps that's too strong a word to use, but that's the way I've felt when a series ended without giving me a feeling of satisfaction.