Simple - to establish her story, her credentials, or "alibi" (take your pick) for use later (i.e. at today's press conference).
Illinois went on Super Tuesday so McCain, Romney, Huckabee and lesser candidates were ballot options.
What we know is she was at a Tea Party event Cain spoke at this year.
It sheds no light on her 1997 claim although documentation should exist regarding her travel, the dinner, the room upgrade, etc. I don't know if Cain denies they ever met.
If the objective facts match, Cain has no way to refute her claim. There are no witnesses when it's two people in a car. Does she have contemporaneous documentation? A police report, a letter, a court document, a medical record... this woman does not.
Two woman who have some historically documented allegations won't come forward. It's ridiculous.
Is Cain a Clintonian cad with more bimbo eruptions to come? Is this about race? Is this dirty politics? It maybe all of them or none of them.
I pray the truth ultimately prevails whatever it may be.