Why do Roman statues have blank eyes?

There were plenty of examples of such statues complete with eyes painted in or even inlaid with glass marbles, jewels or even carved eyeballs. It’s easy to understand how with time the jewels, glass or paint might disappear. Many of the statues with eyes look truly spooky. Google some for fun.

Because they are as old as the Knossos Subspace Portal in Gamma Draconis.

@ragingloli There’s a subspace portal within the stellar interior of Eltanin?

Many marble statues were painted many years ago.

It’s possible that any attempt to make the needed additions would only suffice to make the statue even more lifeless and inexact.

As others have said they were originally painted but the pigments disintegrated over the centuries. Traces of the original colours have been found in some sculptures from Herculaneum.

The paint wore off.

See:

https://www.newyorker.com/magazine/2018/10/29/the-myth-of-whiteness-in-classical-sculpture

https://www.smithsonianmag.com/arts-culture/true-colors-17888/

https://moco-choco.com/2014/04/18/true-colors-of-ancient-greek-and-roman-statues/

I have to wonder if those painted in eyes had big white spots like the characters in anime???

Because those pesky Romans were very poor teachers, their pupils were always absent.

They’re bored.

Because they’ve seen it all before.