I'm not familiar with ceiling fan regulations, but regulations for recessed lighting (can lights) in some jurisdiction mandated connectors other than edison screws in new construction as a way to force out incandescent bulbs.
IMHO, pretty unnecessary, as once the PAR30 dimmable LED bulbs got good, I don't think many people would prefer incandescent. OTOH, I think they were pushing compact fluorescent, which I don't think ever got very good.
For new construction now, the LED fixtures can be mounted without a can, because they put out way less heat, and some of them are very thin, so they may not penetrate beyond the thickness of the ceiling, which is neat. But for retrofitting, putting a screw in bulb is nice and easy.
They don't care if bulbs are replaceable, since their lifetime is limited to build -> sell.