Employers as Agents of the Government?

Why does a person who decides to go into business for themselves and hire employees automatically become an unpaid agent of the government?  All employers are required by to withhold taxes from their employees paychecks and submit the same to the government.  In almost all small businesses the employer is just an individual like any other but because he took the initiative to start a business he has to devote his time to seeing to it that other people's taxes get paid.  Now their is an movement in government to make employers responsible for determining whether an employee is an illegal alien or not.  If an employer hires an illegal alien, even if the employee submits all of the required paperwork, the employer will be held responsible.  If the employer suspects that a potential employee is illegal and refuses to hire him he can be sued for discrimination if it turns out the employee is legal.

Why does the burden of these government functions fall on the back of the employer?  Why do we allow the government to treat an individual who decides to employ other people different than everybody else?  In what way does this encourage hiring or employment?  As a nation we have become so accustomed to this way of doing things we have lost sight of the fact that it doesn't have to be this way.  Let's return to free enterprise, unencumbered by government regulation and interference.  Let's let the United States once again become the free nation that introduced freedom and free enterprise to a dark world.