Why is the old man Winston talks to in the bar unable to tell him whether the old days had been better than times are now?(chapter8)

When Winston goes in to the pub, he wants to talk to the old man and ask him if things were better before the revolution.  He talks to the man at length, but can not get an answer that satisfies him.

What he says is that the man is too old to tell him.  He says that the many remembers too many random details about his past life, but nothing of importance.  He remembers, for example, when he last saw a top hat, but he no longer has the clarity of thought needed to think about a "big picture" question like "was life better before the revolution."

So, the short answer is that the man is too old.