I think Congress and multiple presidents have tended to avoid the issue of any true immigration reform, since so many depend on the status quo as it currently stands. Many have even argued that our economy has grown to depend upon undocumented immigrants, which is quite telling, just by itself.
As a result, neither side really wants to make them all legal, since then they would be entitled to the same rights as American workers (which would mean lower profits for business), nor do they want to deport them, since that would also be bad for business. I'd give Obama some credit for wanting to push harder at going after the employers of undocumented workers, but clearly, there is an ongoing problem which hasn't really been dealt with in earnest.