This is a children's manga? Remember that scene with Obito seeing Rin dead and goes NUTS? Plus all the cussing and other violence...if the manga was translated without censorship it would be rated R. Although the anime is toned down to PG the manga is R.
(Try and put Tsunade cut in half by a tree on the Naruto anime and see what rating it gets)
That's considered acceptable in children's manga. You should check out real adult Manga, it will shock you.
But Naruto's targeted demographic is children, look it up. The rating system works differently in Japan.
Naruto is far from a adult manga, why do you think its got a friendship is magic theme.
Plus as the years have rolled by what is considered inappropriate for children has changed greatly, the entertainment business is always pushing further and further to se what they can get away with putting in cartoons and comics.
But, Shounen isn't big on unhappy endings.