I don't think it's cowardice, is it? The graph at https://en.wikipedia.org/wiki/Leap_second seems to indicate that adding a negative leap second at this point in time would be improper. (We're ~+0.1s off, and a negative leap second would occur if the line was approaching +0.6s. I'd like one too just for the curiosity of the thing, but … the Earth isn't having it.)