This seems like a feature for no one, as the people who really care about leap seconds are probably doing their own timekeeping already since computer clocks aren't exactly accurate to being with.
1. Time is never the same on two different computers.
2. Time is different when you send it and receive it (speed of light).
3. Time isn't necessarily linear (time dilation).
4. Clocks drift, even with NTP.
5. Some systems are isolated enough to accept inaccurate human input and time synchronisation.
Time is an invention for human consumption mainly. Machines are better served with explicit synchronisation (paxos, distributed transactions) or not at all (eventual consistency). Examples in brackets.
Time, if we lose a few seconds here and there, meh, don't sweat it.
Using atomic clocks to sync distributed systems is actually done in practice.
http://static.googleusercontent.com/media/research.google.co...
Even relatively reliable frequency/time standards (HP/Agilent come to mind) aren't 100% available.