The smooth tool removes the work you have done. I am not a fan of the smooth tool either, but it all really comes down to the artist. If you’re working on hard surface sculpting then you need polish brushes (which are just really really soft smoothing brushes). If you’re working on something that is supposed to look worn and faded over a long period of time the smoothing brushes are great. If you’re trying to build out forms it can be okay.
Most artists just prefer that the strokes they make are very deliberate so applying smoothing afterward is a bad way to go.
Oh, the smoothing brush is also a good tool to use as an eraser. Basically…I don’t like what I made, so I’ll smooth it back and start over.
My 2 cents.