Why aren't more countries nuclear?

I mean, they could be if they wanted to. Given the regularity of nuke topics, you might enjoy this.

There are between 40 and 60 states with the technological capacity and economic wherewithal to build a nuclear bomb, and the vast majority of them have decided not to do so, even when there were other nuclear powers in their neighborhood. A few states have started down that road and then turned back, sometimes in the face of international pressure (Libya, Brazil, Argentina), and sometimes mostly on their own (Sweden, South Africa). [...] Iran’s own nuclear program (which began under the Shah) reflected broader security concerns and the Shah's own desire for status, and doesn't appear to have been a direct response to anyone else's bomb. North Korea’s entry into the nuclear club hasn't led South Korea, Japan, or anyone else to start a new nuclear weapons program yet. In short, people have been forecasting the rapid proliferation of nuclear weapons ever since the nuclear age began, but all of those forecasts have been overly pessimistic. More...