A finished deliverable is not always a finished system.
A page can be live and still be impossible for the team to update. An email can look right and still sit outside the automation that sends it. A report can be accurate and still take hours of manual work every week.
The handoff should be designed from the beginning. Decide who will own the thing after launch. Build it where that person already works. Document the few actions they will repeat. Remove dependencies that require a specialist for every small change.
That does not mean every client needs to manage everything. It means the boundary is clear. The team knows what it owns, what support covers, and where to go when the system needs to evolve.
This is also why simple tools often outperform impressive ones. A one-page guide the team uses is more valuable than a comprehensive manual that stays closed.
The work is not complete when it leaves my hands. It is complete when it keeps working in yours.