Sudden Increase In Work Load : A sudden deluge of work could result in your inability to ensure timely performance.   Outsourcing can help take up the slack.

Lack of in-house expertise : Maybe you don't  have the expertise it takes to efficiently handle the work.

Avoid captial investment : outsourcing decreases your expenses on staff and equipment you may not need later.  Face it, computers are the fastest depreciating investments around.