It's gone because they know what they pay for the rights and they know how many people watch the content, and at some point either the rights got more expensive

It's gone because they know what they pay for the rights and they know how many people watch the content, and at some point either the rights got more expensive or the viewership went down, and they presumably get more eyeballs for their buck elsewhere. I would imagine the viewership for old black and white movies is infinitesimal, even if the rights are cheap. The value proposition apparently doesn't make sense.