Printing large volume runs of a production print that is specific and detailed can be a headache when dealing with a third party. Especially now when many companies have a rotation of workers and can lose track of your order and your vision.
When you are a business that produces a high volume of print you often turn to outsource those large print jobs and there is a smoother, more efficient way to work. Especially, in these strange times, it is much easier and safer to keep printing in-house, for a variety of reasons.