I thought the path was originally built to help reduce the congestion on the above ground streets? I work in the core for over a decade and the PATH is invaluable as both an alternative to avoid walking in extreme temperatures (especially in a suit) and a place to eat, shop, and do errands such as banking and dry cleaning.
Since the financial core is so dense, the PATH provides the extra room for the hordes of commuters who need to get down to Union Station. The above ground streets that lead to Union would not be able to support the foot traffic during rush hour without the PATH.
The PATH has been growing for decades and i don't think it has affected the above ground pedestrian traffic at all. During the summer months, people naturally will walk outdoors after being trapped indoors for so many hours. The PATH stores usually consists of convenience stores, food courts, generic brand name storesthat are mostly geared toward quick purchasers. Almost all the stores aren't even open on the weekends. I don't really see the PATH as a shopping destination (yet). Every part of the PATH system is owned by separate entities so there no cohesion or strategy to make the PATH a real mall with a theme or strategy to target the non-office crowd.
The PATH is sterile, confusing to navigate, and extensive. But for the well travelled PATH user, it's extremely convenient to get from Point A to B indoors and a great way to pick up a quick bite or last minute purchase.
