It wasn't Metra's goal, the municipalities along the line wanted it - mostly for recreational purposes. Actually they had asked for both Saturday and Sunday service, but to keep the freight railroads happy only Saturday service was added. Apparently the SWS is pretty bad when it comes to irregular interference at diamonds by the IHB, CN, etc. Once the CREATE projects are done that would clear the way for relatively unrestricted passenger runs on the SWS but who knows how long it'll be until that's done.
That old car might be worth money!