Until recently, employers had to offer insurance, for fear that their competitors would lure away their best workers. Today, it’s the workers who have to compete for the jobs. And if the employer stops offering coverage, the worker can go to the government health insurance exchanges.
Take a look at the Wikipedia entry on the Patient Protection and Affordable Care Act:
Look at the stuff that goes into effect in 2014. Lots of stuff that will make insurance more expensive and more bureaucratic for employers. For a mere $2000.00 per worker, they get to walk away from the whole mess.
Republican conspiracy theorists believe that the Democrats designed it that way on purpose, in order to drive everyone to the government exchanges, and get rid of private health insurance altogether.