Actually, RAAFASA, I do have a rear view mirror!
And have to operate in very congested airspace without the benefit of ATC, and have to lift my wing to have a look before turning......
BUT became convinced of the merit of radio after the glider behind me once advised that I was in conflict with oncoming traffic.......
Right of way? don't count on it! We all have to look out for each other ....every little helps!