Because it's not human.
As computer animation evolved, we noticed a trend. When things are "too human" our brains reject them. They instantly flag it as "not real". When things are cartoony or rough estimations of objects we have no problem anthropomorphizing.
Take a look at this shot from Final Fantasy
Even though it was damn near top of the line CG for it's time something still felt off. It was hard to relate to, it was hard to empathize with.
But Cloud from FF7
Was easy to relate to, even now when his polygon count is silly.
I have seen this effect called "Uncanny Valley" and is simply put, the more human like an artificial thing looks, the more it freaks us out. You can read a bit about it here
So by adding in some offset blinking, and a few other small "irks" that stand out to our brains but not really to our conciseness, the charters are more easily related to and less "spooky".