Old Black & White Movies On HDNet Movies Channel
Actually old B&W movies can, and are, presented in much better than DVD quality by venues like HDNet Movies, a channel whose employees obviously care a lot more about PQ than those at TCM.
When, about 18 months ago I saw the original 3:To Yuma, a 1957 B&W movie on HDNet Movies, the high def picture was stunning. I kid you not when I say that it actually compared favorably with the black & white Schindler's List on Blu-ray.
The thing is, HDNet Movies was founded by Mark Cuban who has been a big booster for HD, and is a picture quality fanatic.
On the other hand TCM's viewership skews quite old, and the powers that be at that network probably think that most of its audience can't perceive better than DVD quality anyway. I even know a 43 year old woman whose eyesight is good enough to play sports but always thought DVDs looked as good as Blu-rays on her 44" HDTV. She finally appreciated the difference when I showed her the Les Miserables Blu-ray on my 73" TV.
Anyway, unlike TCM-HD, channels like HDNet Movies and HBO-HD would probably look very,very good on a UHD 4k TV