Because it doesn't have any state. The only two possibilities are to only send commands related to the device you're activating, or send off commands to everything else. That's not a big deal for my simple example, but what if you have, for example, what I have: a TV, an AV receiver, an additional AV switch, a TiVo, a DVD player, a CD player, a laserdisc player, and a Wii? Then say, for example, you want to watch the TiVo. It would have to send off commands to every other device. And my wife can't consistently point my Harmony at the wall long enough for it to turn on both the TV and the AV switch.


Okay, say everything's off. Then you watch your TiVo and send your macro that includes a DVD toggle signal. Now your DVD player is on. Then you decide you want to watch a DVD and send that macro that includes a toggle. Now your DVD player is off. So you get frustrated and send your Off macro. Now the DVD player is on.

For you and me, this is no big deal. Well, for me it's no big deal until my wife does this and calls me at work frustrated and blaming, and I have no way to look and see what the current state is.