Sativex isn't cannabis, it's THC. There are hundreds of different cannabinoids at work in the actual plant; that's why Sativex is so much less effective.
Children and the elderly don't take steroids, correct, but are part of the population. You really don't see why not including the groups least likely to use it might skew the statistics?
Most steroids aren't taken orally either, and those that are are less dangerous, less potent and extremely expensive by comparison.