Ground bait works by building a patch of water worth staying in. Getting it to the right spot, and keeping it there, is what these tools are for.
By hand is accurate to a few metres and costs nothing, which is enough for margin fishing. A catapult reaches the middle distance and lets you keep topping a swim up without moving. A bait boat carries a full load to anywhere you can see, which matters on big water where the fish are holding well beyond casting range.
Little and often beats one large helping. The aim is to hold fish in the area, not to feed them until they lose interest in your hook bait.