Because the SPDIF digital signal is NOT a matter of the presence or absence of a signal (standard binary). It is the transition from the falling square wave to the next and transition across the top of square wave to the next drop that comprises the binary data. Additionally it is out of sequence to give error correction a fighting chance to keep things straight. You can only see this on an oscilloscope that is rated out to 100 mHz. The rise and fall times are in the nanosecond range and cable quality and correct impedance are key to good sound reproduction. Maybe more so than analog interconnects.
My two cents.
Walt D'Ascenzo
My two cents.
Walt D'Ascenzo