In addition : The end-date of a PhD is indeterminate (at least in the UK), since one doesn't know for sure whether the thesis defense will require any re-writing, etc. So it's difficult to have a job fixed up completely on the day the magic letter arrives.

I chose to travel around Europe for a few months after school and then bothered looking for a job, so I guess by this metric I was unemployed. In the end I left Kansas for a job in London, a much better choice for me than being employed at graduation.