1) Cost
2) Flexibility. If you can hire random laborers to do most of your tasks, you can quickly scale up whereas if you depend on highly skilled and trained workers, starting a new operation elsewhere is hard. Similar, you can shift activity around, are less impeded by the opinions of workers, etc. Significantly, this may allow you to "franchise" your operations in various ways.
Original story archived: https://archive.ph/KBkoK
Sources of interest: https://archive.ph/kG2n8