You can do hard-realtime over the circuit-switched substrate of the public Internet, though. "Two tin-cans and string" (i.e. two modems and the PSTN network) still works surprisingly well for (low-bandwidth) real-time control across vast distances. You can even get a decent hard-realtime SLA (much better than that of wi-fi or cellular data service) when one of the ends is a cell phone on 3G with its headphone jack plugged into a modem.