I used to go on multiday fishing voyages off the cost of California and Mexico. Once we couldn’t see land anymore we’d almost never see another boat. Regular people seldom take their boats out that far, and other fisherman won’t go to the same spot as us.
My father, who was an Alaskan crab fisherman for a decade, would be at sea for months and maybe see one other boat a year. The only times he would is if the crab pots were thrown off course in a particularly odd way which lead different ships to search in the same areas.
I imagine unless you’re growing through the world’s busiest trade routes like the Panama or Suez canal, South China Sea, etc., you won’t see anyone else.