Fairly simple for me - 21 years in the Army; university job in a department that closed after 2.5 years; followed by a stint with a DotCom startup (now bankrupt) which ended with me being unemployed.

Since I had worked as an internal training consultant in the Army and as an external consultant later, it was a natural progression, and I had to put food on the table. A job would have meant a move and major family disruption, so I/we opted for the riskier independent consultant route (five years ago).