To free the company to focus on their core competency. To save time by more easily attracting technical talent as well as eliminating recruiting and hiring functions. To provide the benefit of technical expertise.
Technology is ever-changing.
It would prove challenging for even the most progressive companies to keep abreast of new and emerging technologies. To create a better work environment for internal staff by not over-burdening them and letting technically qualified staff do work that they enjoy , thus increasing morale.