Rather than it being some big corporate conspiracy as you seem to suggest, it may be that Denon, a solidly mid-fi company, has figured out that most of its end-users want to hear their subwoofers go "boom." Source Direct bypasses bass management. Bass Management is absolutely MANDATORY for 99% of the HT-oriented surround-sound setups out there.
Why does Denon 3910 default to PCM for sacds?
I have been made aware of this by Alex Peychev. He states, "Anyway, the 3910 Source Direct ON/OFF mode is in the On-Screen menu in the Audio Settings. You need a monitor. When you select Source Direct ON you have true DSD. If it's OFF the DSD is converted to 176.4/24 PCM. Be aware that the Factory Default is Source Direct OFF, so the machine converts DSD to PCM. You need to go and change that." I have tried it both ways and it makes a substantial difference in the realism of the sound.
I suspect that Denon's indifference to sacd and the desire to hear sacds in dsd conversion is overridden by their expectation that most will be interested in only dvds and HT.
I suspect that Denon's indifference to sacd and the desire to hear sacds in dsd conversion is overridden by their expectation that most will be interested in only dvds and HT.