Each of these services solves a different problem, but the reason to keep them with the same vendor that molds the part is the same across all three: fewer handoffs.
A part that ships to a separate finishing house, a separate labeling supplier, or a separate assembly shop gets re-inspected, re-queued, and re-explained at every stop — and any tolerance or fit issue that shows up along the way has to be traced back to a vendor that isn't the one who can actually fix the mold or process.
Keeping these services on one site means a problem gets caught and resolved by the same team that controls the part's design and tooling, not escalated between companies.