When I lived in Japan, I spent half my life there so I know, what ryuurui, among others, is talking about. It's just how they present themselves that confuse others and make them say, "Then why don't you just leave?"
Once the novelty of Japan wears off, the frustration begins to set in and one develops a love/hate relationship with the country and people. After a while you begin to ignore, and then accept, the things that frustrate you because you can never hope to effect change, and you enjoy the parts that make living there unique and enjoyable. So you stay because the positive far outweighs the negative and you accept it.
Yes, one can feel as ryuurui does and still enjoy living there. I did, as well as more than a few other members presently living there and on this board. One can make a compromise and have an enjoyable life in Japan as long as you KNOW you can never change it and that the Japanese will change at their own pace no matter how much we may disagree with it. After all, it's not our country and we are not Japanese. We may offer our opinion, but it doesn't mean they have to accept it and one should learn to live with that.
There are more than a few things I don't like about where I am presently living here in Tennessee and I do b*tch about it, but it is still enjoyable to an extent and I have stayed here for 20 years because of it just as I did when in Japan. If the negatives outweighed the positives I would have left. The same probably holds true for anyone living anywhere as I don't believe anyone enjoys where they are living 100% and has something to complain about. One must vent frustration now and then to remain sane.
The dangerous part comes when a person truly despises the people and place where they are living, but only stay because they are afraid to make a change or have lived there too long and feel they are too old to make a change, or they stay just for the money. They live miserable lives, forever frustrated, and never fail to let anyone, who will lend an ear, know just how they feel. These people I used to just ignore when I lived in Japan as they are to be pitied more for their fear of making a change for their own betterment. Instead they just bemoan how much they hate their life, Japan, the people, the customs, the food, the housing, etc. without ever really attempting to seriously study the language, culture and people.