Because 90% of systems are a great match for passives, and are the most dynamic /transparent way of getting the source to the amp except for going direct if you can do it without "bit stripping".While the first half of this is false, I do agree that bit stripping is not a good way to do a volume control. You don't want to lose resolution when turning down the volume.
@tweak1 Sorry, I misread your initial post.