Why do fairy tales start with the usual...

"Once upon a time, in a kingdom far far away..."

Because fairy tales can never happen in real life.
They exist in a place so far that we don't even have a name for it.

And only occurs once.
After that, the magic is shattered and
all is gone.
Like nothing ever happened.
Back to the mundane and predictable.

Because fairy tales were never meant to be more than just tales.