Panel testing is very important step in electrical projects; if we skip it or do not do it properly then we may face many issues at the time of installation.
Example :

Missing or wrong ferrule
Missing Components labels
Loose Wiring Termination
Wrong Components Selection
Missing Connection
Wrong Terminal Count  ETC.
Missing ferrules

Due to these the project may not be completed in the target time, this will also affect the quality of the project and result in you not  getting the next project from the clients.