If the black & white channel mixer that is currently only found in Photoshop were added to Lightroom, it would save a lot of workflow time for serious black & white photographers. Channel mixer is by far the best way to convert RGB color to B&W, when maximum creative control and high quality output are your goals. Since channel mixer is not available in LR, you must export an RGB color file and then open it in PS to do your conversion. Although LR has a B&W color editing panel, strong adjustments made there produce noise and halos. If the PS channel mixer were added to LR, it would be possible for black & white photographers to fine tune their B&W conversions while making other LR adjustments at the same time. The end result would be higher quality B&W exports in less time.