Just added six naked light bulbs to the ceiling of my garage and the
improvement in visibility for working is so good that I want to add
three more.

For the six, I threw myself on the mercy of the guy in the Home Depot
electrical aisle: #14 Romex between bulbs.

But when I got home, I realized that the porcelain fixtures used for the
bulbs do not have a ground connection, so the ground wire in the Romex
is wasted.

3 bulbs, 25 watts each... seems like I could just use lamp cord...

Or is there a fallacy in that reasoning?

*For permanent wiring attached to a building you must use an approved wiring
method such as Romex, BX, MC or conduit. That includes installing the
proper size electrical boxes with approved fittings and grounding all metal.
Lamp cord is not rated for a permanent installation. In a garage where the
temperature and humidity is not fairly constant the cord insulation will
eventually dry out and become brittle. Using lamp cord in this manner is
just asking for trouble.

How about posting a picture of this job?