It is always wise to have the hold checked thoroughly before the product is loaded. After all this is where your commodity will stay for some time (weeks even) so you want to make sure that it is clean and suitable to stock your cargo during the voyage.
There can be contamination hiding in plain sight (like rust flakes on the side of the hold, remnants of previous goods stuck in corners, etc…) but also in the closing system of the hatches which can contaminate and discolor your merchandise.
Some contaminants can also have an impact on the quality of the loaded product itself lowering its value and potentially making it unfit for the initial intended use. Checking the list of previously transported commodities is also paramount to ensure the loaded cargo is not at risk. Masters often clean or even paint sometimes the hold before the loading so you want to be sure that everything is dry.
This part of the inspection will ensure that your product will not get no contamination from the holds and not loose thereof its value (merchant and physical value for the intended use). Depending on the port of destination a contaminated product poses a lot challenges in regard of segregation/screening/additional logistic.
In short we make sure that the carrier’s condition is suitable for transporting your cargo.