wree you arawe taht the hamun mnid can raed lkie tihs as lnog as the frsit and lsat leettrs are the smae?

It's due largely to the way the brain is wired to receive information. It only actually works with words that we recognize as wholes and that we see frequently enough though, imposing limitations on what (for a while) was thought to be a rule of the human mind. For instance:

TEHRE

It says there. Did you get it?

FLOOSIH

foolish, right?

ATCCUUURPNE

Anybody get acupuncture?

A vast majority of people will get the first one,  a solid majority the second, and very few get the third. If you got acupuncture, actually, I'm willing to bet you're either interested in acupuncture, dyslexic, or do those scramble things in the newspaper sometimes. Speaking of those things, if you only got acupuncture by trolling through it like those newspaper words, it doesn't count. You're supposed to just be able to understand it instantly. 

Which is sort of how international politics work. (Finally, right?!) There are things that, even when they look sort of wrong, we read correctly because we're used to adjusting for and to the things around us. Not until they look REALLY wrong do we sort of go, 'hrm, how can i fix this'. There are social norms in the global society; don't kill other people's people, don't kill civilians, try to maintain a presentable image, etc. These expectations are often disappointed, and in those instances we have a tendency to ignore it if we can, to "read it" as if it were normal, and hence they aren't really very well upheld. So while we do have social norms and expectations on the global level, they don't really actually serve to limit nations actions until the word gets too big and we are forced to acknowledge its wrong-ness.

speaking of wrong-ness...

Unfortunately, letting it escalate in this manner leads to situations that are exceedingly difficult to repair. (i.e. the well used examples of Stalin, Lenin, and Walt Disney. Perhaps if someone had called them on their extensive power beforehand, we would have avoided the great purge, the red terror, and the inability to get children's movies songs out of our heads.) It's not that we entirely choose to ignore them for our own self interest. We're just prone to ignoring the little anbroalmtieis (abnormalities, anyone?) and assuming they'll fix themselves. 

That is all, lest I tangent more.