Hey Ed -
When we got our R22 we noticed that one of our partners always left the anticollision strobe switched on. We couldn't figure out why... so one of us asked him.
Answer: "It serves two purposes. When you flip on the master, the strobe comes on too, so everybody around knows something is going to happen. Even more importantly, if you look back at the ship after parking and you see the strobe, you know you left the master on."
Doh! It made so much sense to me that I now always leave the anticollision strobe switched on in both fixed- and rotary-wing aircraft.