The profit margins for a single transit is quite small. There might be $100 million in cargo, but the shipping company might only get $40K for transporting it.

The other issue with port regulations is that they aren't really enforced except to provide an (bribery) income for the port master.

I've heard a number of stories of some ports that effectively require bribery to get your ship cleared. If the ship captain elects for the actual inspection instead, the port master will intentionally delay the ship for weeks.