Hi Vishal,
The common answer to this would be that Temp Staffing has its own set of pros and cons. However, much depends on the company hiring such services. Sure, employees are a part of the third-party vendor. Although HR Admin, Payroll, Help Desk, etc., responsibilities lie with the agency, a few responsibilities have to be taken up by the client as well. Regular monitoring, maintenance of attendance, regular feedback to the third-party vendor, etc., are some of the duties to be taken up by the client. Therefore, if used well, this kind of hiring is very useful considering present market trends.
Regards, Imran