I mainly do it just to know that I am 5' from the bottom. I don't have to worry on DR's cable angles or where I am in relationship to the bottom.

I would suppose that the noise would also spark the interest. When fishing that deep there really isn't any light so I would think that fish down there realy a lot on hearing/feeling vibtrions and scent. The noise probably sparks their curiosity, your flashers also produce noise/vibrations while cutting through the water that attract fish.