In the beginning of supercharging, Tesla would place them near restaurants and shopping centers, so you could sit down and have a meal or shop while your car charges. It was a great idea, and still is, but now with the issues of overcrowding they're a victim of their own success. It makes much more sense to have superchargers at convenience marts where you plug in, go inside to buy some snacks or a sandwich, perhaps use the bathroom, and come out in ~15mins as to not drag it out for too long. I believe Tesla has agreements with both Wawa and QuickChek to expand this. If you see a "Coming Soon" supercharger on Tesla's map in a town that has one of these stores, there's a good chance that's where it's going to end up.
Although, the next supercharger opening is at the Rockaway Mall, so it's not a foregone conclusion in any way...