If using a throw-net I could see that right-handers, if they preferred facing forward instead of aft, could possibly have preferred casting the net over the left-hand (port) side, and that have become something of a tradition.
With right-hand screw propelled vessels -- the bow (front end) of the boat tends to naturally swing to the left thus typically requiring a bit "right" rudder to continually counter-act the natural effect of the blades acting differently upon the water (in final result) with a lot of that due to shaft angle (typically at least some amount of downward angle if considered looking aft along the shaft) and the rest being the water further away from the hull is more successfully thrown to the side opposite the descending blade (resulting in more force (of water? can I say 'force of water'?) being thrown to starboard.
Right hand screws will typically back the stern towards the left (port side) too.
I just went and looked it up. They call it propeller walk. I think that may have been a factor for why seiners most usually are rigged to circle to the left, and 'dry up' the net on the left (port side) of the boat.
Modern West Coast squid seiners will often have what they call a "dryer" on the starboard side, but that's for separating the water from the squid (or sardines, anchovies, mackerel, and sometime herring when further North) and so is term for a different "drying".
woops, I meant “world-wide” not would wide.