The US has them because they invented them.

Israel and Britain have them because they derived them from the U.S., an ally.

Russia has them because the USSR stole the design.

India and Pakistan have them because they were educated by the British.

North Korea has them and Iran will have them because they can't bear seeing such a huge discrepancy in might especially not in their favor, and have worked very hard to develop them using information that was either borrowed, stolen or published on the Internet.

A