If you would like to hire IT specialist for your own, it would cost you a lot of money. You should give him full-time employment, life insurance and so on. And how many hours a week he would be needed in your firm? Maybe a few, not more. Thats why, year by year there are more IT outsourcing companies, specialized in network backup.
These are few cons of cooperation with that kind of corporations: they help you to lower an stabilized costs of maintenance of your hardware; you have full access to qualified IT specialists, ready to help you every time of day and night; they can prevent any damages and breakdowns in your system; they provide constant monitoring of most important servers in your firm, and many, many more.
Imagine situation, that during the night, all of your main servers crashes down and you have to find someone to fix in, the middle of the night. If you are hiring your own specialist at full-time employment, you cannot expect, that he will be available all day and night. he may be on vacations, in hospital and so on. But if you are cooperating with one of IT outsourcing companies, there is no problem at all. They have many employees schedules for night and day, ready for emergencies like that.
Cooperation with IT outsourcing companies is not some eccentric costs, but very relevant step, to development of your own firm.