A lot of countries are very hostile to visitors possessing weapons. Boats/ships that dock in multiple foreign countries might have a serious problem knowing when they are in violation of whatever countries weapons laws.
There are many documented cases of Americans being thrown in Mexican hellhole prisons because they innocently, inadavertantly or knowingly carried weapons or even just ammo across the border.
A few of these cases involve weapons on US ships that docked in Mexican ports.
Okay, thank you--that goes a long way in explaining that; I just never thought of it.