Kites hate heights. They don't hate you. (You are running fast enough. There is enough wind. You did put the kit together right.)
You see, they don't trust that string you tied to them, neither the knot nor the cord.
They know the higher they fly, the farther they'll fall. If that knot slips or the cord lets go, they're released and off to places unknown.
Then perhaps you'll find them again or perhaps you won't. Perhaps you won't even look.
And worst of all, if they fly up then break on the ground, they'll not fly again (even if found), no matter how well they soared.
Better to be unopened, safe out of sight, than to let themselves ever love heights.