Why did the immigration reform and control act of 1986 come down so hard on employers of illegal aliens?

The law criminalized the act of engaging in a "pattern or practice" of knowingly hiring an "unauthorized alien" and established financial and other penalties for those employing illegal immigrants under the theory that low prospects for employment would reduce undocumented immigration.

legislative branch:

one of the three branches of government divided between the senate and the house of representatives.

- creates or makes laws

- power to override a veto

executive branch:

one of the three branches of government, headed by the president.

- enforces or carries out laws

- power to veto a bill sent to it by congress

judicial branch:

one of the three branches of government, headed by the chief justice of the supreme court.

- interprets laws

- power to declare laws or actions by the government unconstitutional

which time period is this? or is this story fictional, i'm going to need more info to answer this question