The real reason supporters want to build the Illiana tollway is because the politicians have invested a lot of their money buying up the property around it in anticipation of the proposed Peotone airport. You will note that the plan for this tollway passes right through the Peotone airport area.
Politicians have the inside information years before we know something is going to happen, and it's happened before. Take, for instance, the Fox Valley Shopping center in Aurora; they (the politicians) bought property all around it before it was announced. Another one was the University of Chicago when they (again the pols) bought all the retail property where the university now sits. The other site that was considered was Miller Meadow in Maywood, which all they had to do was put a shovel in the ground and build. There was a lot of discussion about Miller Meadow, but the Chicago politicians didn't own the property so it was not used.
A lot of forethought, years ahead, goes into planning; like the old Chicago post office that was structured to build the Congress expressway under it years later. It's all about the politicians' money and we, the taxpayers, have been and will be the losers.