well, i didn't bother to actually look, or even think very hard but seriously.
Imagine an analogue signal going through tons of interference. You listen to the radio, its all staticy and it never sound really good. The nice thing about Digital signals is it can get as fuzzy as it wants, so long as you can tell a 1 from a 0 your all set.
I'm not saying it must be digital, but it sure makes alot of sense.