Some people try. Some of them even succeed. It's worth to try, but let's not act surprised when the aggregate results look poorly.
Issues like this are, like it or not, best viewed globally, not locally. If you raise the bar until, say, 20% of people can't handle it anymore, then you can go and preach about willpower all day long, but it won't change the fact that every fifth person simply won't have it, and it's not really their fault.
It's hard to pull yourself up by your own bootstraps if you weren't born with them (and not everyone in the world is). Acknowledging reality does nothing to dissuade people from trying their hardest, but sometimes one's hardest isn't enough.
