A false equivalence has been generated in these last posts. Although not stated explicitly, the implied message is "Some people who dive without training die, but so do some people who have training; therefore, there is no benefit to certified training."
Of course, the problem is the vagueness of the word "some," which could cover a range from 0.00001% to 99.99999%. Is 0.003% about the same as 99.97%? Of course not, but if you call both numbers "some," they sound about the same.
Now, I haven't got a clue of the actual percentages, but I do recall a thread a few years ago in which it was reported that roughly 50% of the people who die in cave diving accidents are certified to dive in caves, and 50% of those who die are not. To people who do not understand math, it sounded like there is no benefit to cave certification, and several people said so. Of course, the fact is that probably about 98% of the people who go into caves are certified, so the 2% who are not certified are providing 50% of the deaths. That makes the difference significant, although a lot of people still would not understand why.