We might be confusing "in the floor" with "ON the floor".
Floor boxes, and their covers, are evaluated with a lot of attention given to "what happens when the floor is mopped or the carpet is cleaned?" Likewise, it is assumed that the receptacles will be in the middle of the floor, for all to run into.
Remove those concerns, and then the remaining worry is "what about falling crud?" I think you can see why the NEC bans 'face-up' receptacles in kitchen counters.
I think a case for mounting receptacles on the floor, face up, where protected by furniture can be made. Think of that cord dropping between a desk and the wall; the plug is certainly more likely to be damaged (by the desk pressing onto it) coming out of the wall, than coming up from the floor. While there might be a possibility of someone spilling their coffee' this risk is not even in the same league as a kitchen counter (which is deliberately made wet and dirty, regularily).
I see this as a design issue. Plugmold on the floor, behind the sofa? Sure. Plugmold on the wall, along the jacuzzi? No Way.
