Automating ATC is similar to automating flying in general. Even if it's possible to automate 99% of 99% of flights, including even takeoff and landing, commercial flights still have two pilots because if things start to go wrong there's just so many edge cases that you can't easily write automation to handle all of them. Same thing for ATC, except even worse. They still have control towers because controller eyeballs still work even if nothing else does, if ground radar fails, or if a vehicle doesn't have an ADS-B transponder, or if a crash eliminates the radios, etc. There's just so many edge cases that making automation be able to handle everything is extremely difficult