I would like to add that max gain should be used in conjuction with some tilt manipulation to give a pilot best understanding of the weather ahead.
In the early 90's, The A330 radar is so useless that what should be red showed up as scatted greed dots. So, we have to repeatedly tilt it down to minus 8 the move it up a notch every sweep. Using simple 1-in-60 rules, we learn to read the cloud and manage to make a smarter guess of where is the top of the nasty bit where anything on top of that should be ice crystals. That help to decide how much to avoid or what can go through. Those monsters sitting over Indonesian airspace gave many good practices.
Used the same method in the B737 and B777. Works even better as these radars are more accurate.