In the last momensts before totality, when the sun is 99% covered, you still have more light than a brightly-lit room. It's roughly the same light-level you would have if you were standing on a moon of Saturn.
When totality comes, you're going from well-lighted-room to darkness - but only for a couple of minutes; and you're spending a significant amount of those minutes looking at bright things like the solar corona and the horizon.
Your eyes simply do not have the opportunity to adapt enough to see stars.
I've seen two totol eclipses, and both times I was too busy screaming and jumping around to even think about looking for stars. I'll probably be the same way in 2017. I can see the stars on any clear night. I'll want to be looking at the corona & horizon!