There are a handful of coffee shops that actively don't want to be used by laptop/tablet users, and one way they signal that is by not offering wifi. It's not quite as effective a deterrent as it used to be with the advent of cheapish mobile data plans that have tethering, but it can give you an indication of what the shop expects its usage to be. Fins Coffee in Santa Cruz, CA is an example of a shop without wifi.
Given how heavily Starbucks not only offers but advertises its free Wifi (as does McDonald's), my guess is that they do actually intend their stores to attract laptop/tablet users.