Time

First and foremost it takes time to keep up with all of the regulation and payroll tax requirements  changes.

Money

The cost to outsource to a service should not even come close to the cost of an employee.

Accuracy

If the employer has done their homework on researching a good payroll service, then they should have peace of mind in knowing that their payroll is being done accurately so they can avoid penalties and interest being assessed on their payroll.