Even if that is the case, jobs now change at much more rapid pace than in the past. It used to be that if you trained and worked as a blacksmith (or whatever), you could die a blacksmith. It was their kids that would have to do something else. Which isn't too much of a shock to the system.

This is no longer the case. Now someone within a single lifetime can go through multiple job creation and destruction cycles. So it'd be helpful to have a floor to help deal with the transitions and provide a buffer.