I also notice this. If you keep roads safe and local militia doesn’t get wiped locations are full of supplies and weapon.
Check the status under the name of location in the location screen.
Wealth is used for generation of caravans and military forces. So if they lost caravans they not only lost future profits but also chunk of currents wealth. The same goes for military. If they get losing troops they need spend wealth to replace them.
Poor location = poor military forces = no chance to protect caravans => poor choice of items. Only you can safe them after some point.
