This is something I've long wondered about myself. This conundrum accelerated me to old-man-yelling-at-the-radio stage yesterday listening to the Sunday talk shows while out doing errands.
Bernstein has his potential answers here. In abbreviated form, they are:
1. People believe the Recovery Act didn’t work and have turned anti-Keynesian.
2. Deep misunderstanding of the role of deficits and debt in contemporary economies.
3. Faux deficit concern as a tool to shrink government.
4. Fiscal policy we can (theoretically) control, but no one really knows how to generate job creation.
Number 4 is closely related to the "we have to do something!" reaction (do we? really? maybe we don't have to do something about the deficit but it's worth doing something about jobs).