It's the same reason you take the escalator instead of the stairs, or the moving sidewalk instead of the stationary one. Why work harder than you have to?
It is easier and faster for ships to sail with the ocean currents.
Ocean currents will carry anything from small plankton accross ocean to helping other marine life find warmer or colder waters. to ocean currents can also help guide ships across bodies of water. the ocean currents will also redistribute the density in the ocean water.
The most common type of ocean pollution is garbage or sewage. They are readily dumped into the ocean by ships and countries located along the ocean.
Arab traders sailing the Indian ocean in their sailing ships preferred to travel during the months of June and July because they were the prevailing months of monsoon winds; that is why they are called trade winds.
trade winds
The routes that ships follow are called Sea Lanes. These lanes help keep the ships from collision, are the most direct routes from point A to point B and although may not be the straightest route, they are the safest and fastest. Many Sea Lanes follow existing sea currents.
Ships stay away from the bottom of Niagara Falls.
There would no longer be any need for canals like the Suez Canal and Panama Canal. Ships could simply sail directly from ocean to ocean. Huge changes in sea life would be expected as ocean currents would change considerably.
There are about 80,000 ocean-going ships in the world.
Because that is where the colonists established the colonies. The currents took the ships from Europe to the east coast.
Dhows and junks (large ships involved in maritime trade in Indian Ocean) from China and other South Asian islands traded with India
It is impossible to know how many ships are on the ocean at any one time. This is because there are several oceans, along with thousands of ships, military vessels, trap steamers, cutters, and boats. Only the registry for each boat can determine how many other boats are in a respective area at one single time.