My theory is that manufacturer's don't want their products to have a performance disadvantage to their competition. OSD displays degrade the video quality passed through because they have to overlay a generated transparent layer on top of the video image. For menu functions, this is probably ok, as it is a setup routine. For volume display, something that would be needed during normal operation, the manufacturer has 2 choices.

1) switch the overlay on only when volume display is needed. there may be a slight disturbance when the overlay is activated and some end users might complain if they notice this or notice a picture degredation while their volume is ramping (quite a minority, I'm sure).

2) leave the overlay on at all times. While I do believe that the masses would be quite happy with this solution, it leaves yourself open for critical feedback from reviewers and the more discerning client. Many companies will not use a product in installations at all if they fail any similiar criteria. I think to use the always on feature on component video would be a very bad move and grounds for dismissal to the AV component hall of shame.

I think that there was 1 company's unit that did it the right way. There was a monitor output w/ OSD, a monitor output w/o OSD, then a record output. I don't remember who it was, but it might have been the Integra DTR series or McIntosh pre/pros.