Theoretical Korean Standard 'Modesty', Or Is It Just Less Living?

'겸손함은 생존전략. 그러나 편하게 살면 덜 산다'?

My dad came up with a theory of why Korean never say they know what to do with their lives or boast about what they can do, even though these people got potential nothing short of the geniuses.
Modesty?
Survival tactic, he said. If they say they can do something, and if someone ask them to do it, then they have to do it. But what if it was just another 'easier said than done' scenario?

I agreed it make sense. But I disagreed that's how it should be done all the time. About being afraid of failures and not living enough too busy surviving.
To a tyranic bossy bosses, it make sense. No one wants one of those sucking a life dry out of anybody. But to a friend or team members who's suppose to work together? Or are all Korean expected to be a capital vampires?

Beside, if one practices some easier lies long enough it's all going to turn into the reality at some point. If once they pretended they can't do anything, they're going to end up really not be able to do anything, and only do what they've been told to do.
So that's my theory.