Automated call screening feature to block automated dialers

I grew up with an uncle that was hard of hearing. I had gone home to visit him when he was in his 70's, and his phone rang. He didnt react, just continued telling his story. A couple rings later I thought maybe he couldn't hear it so I told him it was ringing.
He simply said I know, And then gave the best view of how to think of it that I ever heard.
He said "I put that thing in for my convenience, not someone elses."