[lazide]

If you have a group of 10 random people, you'll have to count on 1-2 of them not knowing something important you think everyone knows (if you're lucky).

If you have a group of 100 random people - that's now 10-20 people. A whole team, maybe two if the cards are particularly bad.

The Army has 479, 000 people. They also have significant, predictable turnover, so if they teach everyone all those things once, in 4-5 years no one in some military specialities will know it again. Based on the average time in service (6.7 yrs) data I can see, even if they teach literally everyone everything they might not know that is considered essential, in ~ half a decade at least 1/3 of the people in the Army won't know some or most of it again.

Add in that people can only pay attention to and retain so much, and you have to repeat things a lot, explain things from a bunch of different angles, and then test and validate on top of that before you can assume they know it.

Even then, they might forget in a week.

It's law of large numbers and people.