I like to take a first wort gravity reading, and compare to the theoretical first wort gravity. If they match, I'm good, otherwise I don't have full conversion so I know I had better look for something amiss.
I also take readings of second and third runnings. It would simply be impossible to do all of that with a hydrometer. By the time the sample was cool enough, I would have moved onto the next step, without having time to adjust if I catch something awry.
Once the runnings are in the kettle, I put away the refractometer, but both tools have their place in my brewhouse.