And also it give them time to work out the bugs in their ancillary programs such as exchanges, fee structures, ect. to make sure that when it is fully implemented that there will be no chance of repealing it, or it being repealed. If it was a gambling endeavor, it would be known as a sucker bet.
Once the generous subsidies kick in for lower-income people, there’s no way this thing will ever be repealed, short of the GOP holding the Congress and the White House.