until a shuttle blew up, there was no risk to using o-rings in cold weather conditions
until a shuttle came apart on re entry, there was no real risk to chunks of ice hitting the shuttle wings during lift off.
until there is no collision or other interaction with full scale above 400 ft, there is no risk there either,
but there is NO guarantee that it will not happen tomorrow, either.
one thing about life,
just because it has not happened yet, does not mean it will never happen.