"blocks and tackles are what makes it possible to raise and lower immense surfaces of canvas in storms and rough seas with nothing but our arms and plenty of grit"
Cpt. A.C. Kromann (the fictitious version of him)
Imagine pulling a 20 kg sack up from the ground with a rope running through a simple metal ring attached to a beam overhead. It feels as heavy as 20 kg ought to feel. But pulling the same weight with a gun tackle, and then a double tackle is fascinating. You have to pull in a lot more rope, but the weight is so light compared.
For this reason, they were and are still used on sailing ships - often so numerously that riggings look like cherry trees with the blocks being the fruit. On a two mastered schooner like the Flora, there was enough to become a major production issue if not implemented in a tolerably flexible way when building the 3d ship.