Reply #13: How about this reason:

[The Straight Story]

This paper is a history of the Israeli nuclear weapons program drawn from a review of unclassified sources. Israel began its search for nuclear weapons at the inception of the state in 1948. As payment for Israeli participation in the Suez Crisis of 1956, France provided nuclear expertise and constructed a reactor complex for Israel at Dimona capable of large-scale plutonium production and reprocessing. The United States discovered the facility by 1958 and it was a subject of continual discussions between American presidents and Israeli prime ministers. Israel used delay and deception to at first keep the United States at bay, and later used the nuclear option as a bargaining chip for a consistent American conventional arms supply. After French disengagement in the early 1960s, Israel progressed on its own, including through several covert operations, to project completion. Before the 1967 Six-Day War, they felt their nuclear facility threatened and reportedly assembled several nuclear devices. By the 1973 Yom Kippur War Israel had a number of sophisticated nuclear bombs, deployed them, and considered using them.

http://www.au.af.mil/au/awc/awcgate/cpc-pubs/farr.htm