I was just a kid & couldn't figure out why he quit. I'd say, "What's he going to use his arm for in his 50s?"
Well, there's a contemporary answer.In 1966, another immortal had a sore elbow - Johnny Unitas. He played through it. The next year it was a little better & he was MVP. In '68 his elbow basically exploded. Yet he came back. He had trouble signing autographs and gripping the ball, but played 5 more years. He gained most of his arm strength back and led the Colts to some of their greatest years. But he was ALWAYS in pain.
By the time he was 55, his arm was useless. He'd lost a couple of fingers. Maybe it was a factor in his death.
Sandy made the right decision.