That can be said about any survival skill: hunting (e.g. shooting, searching), identifying non-poisonous mushrooms or plants, knowing how to make fire without dedicated tools, surviving in cold climate, hot climate, sea and etc. You simply can't know everything. It is nice to know these skills but there is low probability that you will benefit from them.
Only 20% people in Hong Kong (and I believe mainland China) know how to swim - doesn't look like a problem for them.
