They were never common but showed up for a short while around the turn of the century in the form of an adapter + lamp (GE I think was the only manufacturer) and in torchiere lamps. I think circlines were still more popular.

There's a building at my university with some huge recessed fresnel lights, a few of which may still have working 2D adapters in them. I know I saw them a few years ago. Now, most of the lights have LED PAR38s.