No, that wasn't the question, why does it seem a team with better xG lose/draw a game an inordinate amount of times.
What does it add to anything that can't be understood/observed already by watching the game.
"We were all over them, but we could have played until midnight and not scored" you can see it and giving it a number serves no purpose.
It's assigning a statistical probability to something which is way too variable.
I can see some value assigning it to players as a measure of how clinical in front of goal they are, even then though you've got "he scores that 9 times out of 10" or "he couldn't hit a barn door" which you can see for yourself.