Most companies want to control access to payroll. Intuit has designed payroll to work in single user mode.
If you have QB Enterprise, you must log in as Admin, and switch to single user mode to setup, manage, and process payroll.
For smaller companies this may not be an issue. For larger companies with multiple payroll clerks it could become an issue.
One way around this is to setup a separate company file to handle payroll.
Intuit assisted/full service payroll will work with handle 150 employees. If you have more employees you may need more than one company file.