I like your point about factoring challenges and having alternate plans. Many things can happen in life to cause a job loss. Anything from a health problem and disability to the company one works for merging with another company and firing workers. It does seem that some careers/jobs have a little more security. As I understand it, tenured professors can't be fired. Of course, many other problems can still befall them. Then you have those who are self-employed who can have gaps in their income just because of the nature of their business or work.