Can't do that for one off large scale projects. You can't hire in a bunch of brand new people only to lay them back off after the project is complete without blowing a ton of time and money. Spending time to train them to take on the project in itself would be a huge resource sink. In cases like this where it is a project rather than a new division, you have to scavenge from within your current asset pool. It's just the way companies have to operate and part of being a business before anything.