The expertise sits outside your team.
For a task you plan to bring in-house, the practical explanation may still depend on an external specialist. A service handover needs to address usable knowledge as well as documents. Time lost waiting for external answers.
Every new starter needs the same explanation.
When onboarding depends on a few experienced people, adding technicians also adds to their teaching and support workload. Expert capacity lost to repeated explanations.
What one team learns doesn’t reach the others.
Findings and the context behind them can remain in individual memories or scattered records. The next team then has to reconstruct what happened. Knowledge lost between teams and handovers.