To refresh, the five villages are Iga, Banten, Fuuma, Togakushi and Koga. The reason they all still exist and haven't wiped each other out is mostly because each has a kinjutsu, a forbidden or secret technique. They're hard to learn and very dangerous to the practitioner, as far as I know. They can't be shut off, they're hard to combat, and trust me when I say someone who's mastered one of these are leagues better than any other singular ninja. Often better than several combined.

[has he built up the suspense enough yet]