Cable... reducing a cable. I have 3 cables going to my monitor: a power cable, I need that still; a USB cable, because I have USB ports on my monitor; and the monitor cable. I would still need one cable for power, another for the USB. I would eliminate one cable.
This wouldn't help my TV either. I have 2 cables that go to my TV; a power cable, and an HDMI cable that plugs in to my revceiver. You can build a portable MAME rig right now, you would need to have a power cable, a HDMI/VGA/DVI port and that's it.
The laptop idea is not applicabple as the laptop is a self contained unit, a mame rig you have to hook up to a monitor, you are going to set it up in offices and living rooms, you aren't going to take it to the park on a sunny afternoon.
Seriously, its saving ONE cable, its not a big deal