Well ofcourse it dosent but I honestly cant see the developers implementing a hand animation to wipe away the dirt/ adding a blinking animation just for this purpose.
They woulden't have to, from your own 1'st person perspective, you won't see what your 3'rd person model is doing, so all they have to do for blinking is apply some basic filters to the screen to create the effect, no need for animation work there.
And people around you who can see your 3'rd person model, won't know that you got something in your eye, because they can't see your 1'st person view, so it doesen't really matter if they see a blink anim or not.
Sure it would be a nice feature if they did animate it, but hardly worth the time to make, time that could be used to make so much else, a 1'st person view filter would be plenty.
EDIT:
Ohh don't be like that, this isen't rivet counting, just a little touch that could add some immersion, i think it would be neat if getting a face full of dust/dirt/whatever actually had some kind of effect on you, like blinking, it would make you feel more connected with the world, and it would be easy enough to do, no harder than making thouse silly "blood on the lens" effects every other game has.