Field Frame

The mistake

Removing the visible borders from form inputs strips away the affordance that tells users where the editable region is. A label sitting next to nothing looks like static page text, so there is no cue about the click target's location or size, and the field only reveals itself once you happen to click in the right place. Labels name a control; they don't indicate that a control exists or where its boundaries are, so the border is carrying real information rather than decoration.