In Star Wars, hyperspace is the main way of travel. It's used by the Rebel Alliance both as a way to attack and to escape.

Quite understandably, the Empire created Interdictor-class Star Destroyers. Those starships where made with the sole purpose of preventing other starships to go into hyperspace.

But even though those ships exist, they barely saw any use at all, especially in battles where their presence would have changed the outcome of the war.

The most damning example that come to mind would be the Battle of Scarif. At that point, the Empire knew that a fatal weakness existed in the Death Star. So when the Rebels attacked Scarif, where the Death Star's plan was stored, it was pretty obvious what they were aiming for. So the Empire sent a massive amount of reinforcements, which lead to the rebels getting decimated. But a Corvette still manage to escape and enter hyperspace.

All the Empire needed was one Interdictor, and the rebels would have never had a chance to win, because the plans would have never left Scarif.

Obviously, the easy answer would be that there wasn't any Interdictor available close enough to the battle to make it in time. Which would raise another question, why was such a vital ship, that can completely corner an enemy and cut off their only escape route, not a mandatory part of any and all fleets?

Why were the Interdictor-class ships, which provided an incredible tactical advantage, almost never used?