Old Man and a Pawn

I've never been a good chess player. It was a lack of school from the childhood. I was quite a good international draughts player, though. And some of my friends were really good chess players that learned to play from very young age in the Palace of Pioneers' chess club. This is the story told by one of them.

Once an old man came to the Palace to play chess with kids. And it happened so that at the end of the game a kid was left with white a4 pawn while black's king was standing at a2. Nothing could prevent the promotion of the pawn, so the kid was expecting a resignation. But the old man made his move Ka3, and the kid started to suspect that his opponent knew some trick. Yet no other strategy was available, so the kid played a5. The old man moved his king to a4, the kid played a6, followed by Ka5. a7, Ka6, a8Q! Then the old man sighed and said: "Too late!"

How so often I play such unnecessary moves that don't give me anything and have the only virtue of being forcing.

Wasted ko threats  

In the frustration that I failed to kill I play . White, naturally, replies with , I capture with and white replies . Then I say to myself "Too late!"

But I've seen that this was coming. Why, then, did I play it?