This weekend, a leap second will be added to the official time. This is due to the fact that the Earth is slowing down and our clocks would gradually get out of sync with the day length if we didn't add a second or two every so often. Thus, you get an extra second to sleep this weekend.
However, scientists are debating whether or not we should continue to try to keep our clocks in tune with Earth's day length. Of course, if they stop adding seconds, eventually the sun will start coming up in the middle of the night, so it could be a bit confusing for some folks.
Still, if all of humanity remains on Earth, eventually something cosmic will kill all of us, just as it did for 99.99% of the species on Earth. We have been extremely lucky to have survived five (count 'em—5) extinction events which wiped out most life on this planet in the past (Yay! We're all official survivors right now). Eventually, our number will come up and all human life will be eradicated on Earth. The odds just demand it.
Consequently, why should people living on Mars or on space habitats drifting through the solar system care what time it is on Earth and that a second has to be added to the clock? If the future is bright, the leap second should be abolished. But, if we decide not expand into the solar system, well, we should probably keep the leap second as a reminder of our vulnerability.