Because the devil is in the details. Many Americans seem to believe that passing a law solves the problem. It doesn't. Few people are focussing on what kind of resources will be needed to enforce the laws on the books or those proposed. I had lunch yesterday with a former BP agent who served nearly 40 years on the job and with a former Deputy Commissioner of INS. The numbers of personnel assigned to enforcement of our immigration laws against employers are less than 400 hundred.
The entire enforcement system is crumbling. It is going to take a massive increase in personnel to fix things. And it will take years to build up those numbers with trained, experienced personnel. The proposed Senate bill will create a staggering workload that can't be met by the existing bureaucracy, which is alread backlogged. Passing laws without the resources and capability to enforce them is meaningless and we have already seen how that works.