I have never had the need to use them. Using the correct blade, saw speed and feed rate for the wood you are cutting, you shouldn't have to Sand except for the fuzzies. If you mis cut, it's easy to go back and clean up the cut with the blade. I use the right side of the blade to clean up a mis cut. The right side of most blades have a bur from the manufacturing process. This makes them somewhat sharper than tha left side, perfect for touching up a mis cut.
Using the right blade should produce a clean and smooth cut edge. On certain hardwoods like Cherry and Maple, the cut edge will even come out shiny.
What is the right blade? That's dependent on the type and thickness of the wood. I like mostly flat, skip tooth blades. I use the smallest size blade to cut the frets or inside cuts but big enough to handle the thickness of the wood. So you have to experiment with what works for you.
One of the most important factors is to be as accurate as possible. I like to split the line. That is not cut to the right or left of the line but down the center. When you go off the line, make a gradual return to the line, not an abrupt return. This will prevent those ugly bumps that need to be sanded out.