I thought this too...
...until you consider a few things.
The post above says it all, really, but then again, often airports are not in the best neighborhoods.
And yes, there is public trans. via the Chicago/South Shore railroad, but the main way to get places for most people is probably by car. And if you've ever driven I-80/65 or I-80/90 near the IL/IN border, you know it's miserable -- more truck traffic than anywhere else I've seen, and one direction is crowded 24/7. That's reason enough for me to stay far away from Gary.
Pan Am tried it, not sure if they still fly there...it's too bad really - the one that should be utilized, IMHO, if people are willing to drive to Peotone and back is Rockford - RFD - almost the same distance as Peotone, a little further -- but the interstate and all the infrastructure is already there. Rockford is an absolute ghost airport, sans a few practice approaches and corporate traffic until 10:30pm when the UPS aircraft start arriving.
Take care,
-brew3