These rigs are used all the time in salt water. I have used them on fishing boats in Florida. They are sometimes uses just as Chris said, but in the salt, most of the time they are used as teasers to get the fish up so you can cast to them. They do resemble a school of bait fish. There is also a rig with 6 small fly type hooks that hang straight down, its called a Zabinki rig. I have a couple of them in my kit. They are used to catch bait fish. I spent several years as 1st mate on a fishing boat in Florida when I got out of the Navy in 1971.
If you're too busy to go fishing, you're too busy!