The right to arms is in the U.S. Constitution because the United States were formed from the rebellious colonies of a great military power. The rebellion was started by the armed citizens of those colonies, and was overwhelmingly fought by those same people, many of whom went home afterward and took positions in their new governments.

Why does no other nation recognize an individual right to arms? Because no other nation on Earth was formed around the idea that governments exist to preserve the rights of their individual citizens. That, when governments fail at this singular task, it is the inherent right of those citizens to "alter or abolish" the existing government and replace it with one that works. And that government should not have a monopoly on violence, rendering that inherent right moot.

Ninth Circuit Court of Appeals chief judge Alex Kozinski wrote cogently in one of his better dissents:

The Second Amendment is a doomsday provision, one designed for those exceptionally rare circumstances where all other rights have failed - where the government refuses to stand for reelection and silences those who protest; where courts have lost the courage to oppose, or can find no one to enforce their decrees. However improbable these contingencies may seem today, facing them unprepared is a mistake a free people get to make only once.

With the singular exception of the United States, every other government throughout history has risen, not to protect the rights of its citizens, but to protect the power and privilege of the powerful and privileged, and expand that power and privilege as much as possible.

Unfortunately, human nature being what it is, our government has succumbed to this disease as well, though it has lasted longer than anyone had a right to expect.

Freedom is messy. Freedom is dangerous. But freedom is the engine of creation (and often creative destruction). It's no wonder freedom is opposed by all "right-thinking" people who gravitate to government in order to preserve their safe, comfortable status quo.

And get a little for themselves on the side.