Because the Tesla stuff is just a spiffy looking "dumb" post, there's essentially nothing to protect in there as all the actual supercharger electrical hardware and smarts are in the cabinets in the equipment pad area. Plus, there's no serious electricity running to those posts until you plug in and the car and cabinet do their handshake to initialize the charging session. The Flo unit, on the other hand, is the charging hardware as well as the connection point. It and that small transformer next to it are permanently energized with "high" voltage regardless of whether a car is plugged in or not (note this isn't true of the charging cable/plug on the Flo unit but the cabinet internals), and since they are sited close to driving areas, they need more protection than Tesla's dumb posts.