If nothing else, putting a legal end to the "anchor baby" racket might suggest to the American public that they were regarded in Congress as something more than expendable suckers who can be mollified with rhetoric.
Waiting until the border has already been secured before an immigration policy is decided upon would also allow time to discuss the pros and cons of various ways of enforcing whatever that policy might turn out to be. But many politicians much prefer to rush complex legislation through Congress before the public knows what is in it or what is at stake. "We the people" are to be by-passed.
Time to deliberate would also be time to raise questions as to why local government officials in "sanctuary" cities who openly thwart or defy federal immigration laws should be allowed to get away with such illegal acts, while private employers are forced to become enforcers of such laws, under heavy penalties for not investigating the legal status of those they hire.
Government officials at all levels take an oath to uphold the laws, but somebody who owns a restaurant or hardware store has not applied for the job of border enforcement -- and the 13th Amendment forbids involuntary servitude. Or are we already too far along on the road to serfdom for that to matter any more?
"Comprehensive" immigration reform serves the interests of politicians who like to be on both sides of a controversial issue, and it serves the interests of those foreigners who want to game the system in the United States, at the expense of the American people. But it does not serve the interests of American society.