Charles not working on iPhone at Starbucks

Client isolation. It is your enemy and your friend here. This makes it so not only can you not access your iPhone from your MacBook, but other devices on the network cannot access your MacBook or your iPhone either. There are a number of ways to implement client isolation on an IEEE 802.3 (Ethernet) network and even more ways on a IEEE 802.11 (Wi-Fi) network, but they all essentially accomplish the same task - clients are only allowed to communicate with the access point and/or gateway.