To get to that, we have to first think about the literacy rate in antiquity, which is estimated at 5 to 10%. And of those, most could probably read well enough to get by, but didn't routinely read longer texts. So someone who was well-enough versed in reading to not have to read the text out loud in order to understand it was probably a rare and noteworthy creature indeed...
I would imagine most reading would be "let me read that sign" and not much else. To most folks, writing was probably logographs - "Ah, I've seen that collection of letters before, that meant 'pub' "
And you can't read long texts if there aren't that many to begin with. But it raises a question - why didn't China, which invented printing press earlier, didn't fare better?