I know without researching a thing that the infrastructure has been under construction for four years and the exchanges are ready to open in two days. During that time the average citizen has been shielded from any direct affect of the law.
The equation is simple; a delay gives the administration one more year to build infrastructure while the people are shielded from its pain for one more year.
The people are NOT shielded from it. People have had their work hours cut and lost insurance coverage. It's already a disaster.
If it gets a toehold it's here to stay. Bank on it!