Yes it would be a little harder to lock a lable to a wire but you still have segment endpoints to lock to
the algorithm could lock the bottom of the lable to just above the midpoint of any two endpoint segments and allow
for unlocking and hiding of lables. I dont think it would be so hard. Since the text lable es already capable of orientation the lable could automatically go clockwise or ccw for verticle wires (up or down). This is a big time saver for resizing diagrams.
If NI ever did implement wire labels, I would have to assume the default would be not to show them. If you're using enough wires that you can't just label them individually, I think all the wire labels would be at least as confusing, if not more, than following the individual wires. I also still don't see how wire labels are better than clusters.