Why are we supposed to act like we don't care who wins, when we actually do care?

My 6 year old granddaughter had a track meet yesterday. She was in the long jump and the 100 meter dash.

In the jump the kids got 3 chances to jump. Her first jump nailed 4 ft. even. She was the first to break out of 3 ft.
Her next jump was 4’ 2”.
Then a little girl jumped 4’4”.
I said to my daughter, “This last jump has to break 4’4” for first place!”
My daughter said, “We don’t care about that. We only care that she’s having fun.”
Well, who went craziest when she blew everyone out of the water with 4’ 7” on her last jump?! :D Spring loaded, just like her mama was. I knew she’d do well.

She was also in first place in the 100M dash…but wiped out half way through the race, like Cool Runnings. Road rash ouch. Poor baby.

So why do we insist that it doesn’t matter if they win or not, when it actually does?
I get that it’s not worth making a kid feel shitty or like a loser if they don’t get first place. I get that there are some people who obsess over themselves, or their kids winning, and I agree that’s not healthy. But generally speaking, for non obsessive, normal people, why are we supposed to act like we don’t care when we do?