... you still believe that the leading expert at ADAM and Yamaha and SPL and all the other manufacturers have just created this range out of thin air to use as a marketing tool.
ADAM, Yamaha and SPL did not invent the format, as far as I know the first to support this format were DigiDesign. I can't remember off the top of my head the name or composition of the standards organization responsible. I should also mention, that professionally we've been using higher than 16bit for almost 20 years, although it's only relatively recently that it's been called Hi-Res and there has been a consumer demand for it. Now there is a market, I cannot blame Yamaha or ADAM for taking advantage of it, even if the demand is almost entirely superfluous for the consumer. If you are talking about professional studio monitors, then as mentioned previously 24bit is useful for recording and mixing, it's as a playback consumer format that 24bit is irrelevant.