The employer needs to know the complete address of the employee for a number of reasons. One is for payroll purposes. Setting up an account for a person requires him to provide his address. Another reason is that if something wrong happens, they would know where to locate him or his family. The company also needs an employee's address so that they can be certain of his identity. And another reason would be for mailing of anything necessary purposes.
The social security number will be part of the template. It will provide the company everything it has to know about the employee. If he has an outstanding warrant of arrest from the police, if he is an outstanding debt, what responsibility he has, what violations he did, etc.