I have eaten at Luke's for some time now. I am not from Chicago so I can't offer any feedback on authenticity but it is usually pretty good.
I am not sure what's up with the owner. I assume him to be the salt and pepper haired guy who appears to be in charge. No one working there seems happy and like many other reviewers have already said the fat dark hair man working the counter is a business killer. I would have to guess he is driving off 10s of customers a day minimum. The owner is either blind or just doesn't care because the rude treatment goes on when he is right there.
Time for Luke to thrown in the towel or make some big changes. Start by firing the rude #%ck at the counter.