[chrismaeda]

One answer is accounting rules. In a typical IT shop that supports a business...

Spending for "business as usual" (BAU or "opex") activities must be fully expensed in the year that it happens.

Spending for capital projects (new IT systems and upgrades aka "capex") can be amortized over the lifetime of the project. So if you spend $1M on a new IT system, you might expense it over a 5-7 year period.

So IT organizations will only have permanent staff for BAU and will hire temporary contractors for capital projects.