It might seem like controllers are not that necessary but (similarly to pilots of modern airliners) they are very important when stuff doesn't go as planned. Pi

It might seem like controllers are not that necessary but (similarly to pilots of modern airliners) they are very important when stuff doesn't go as planned. Pilots can take over a and pull a Sullenberg, controllers can provide pilots with information on speed and height in case their instruments don't work (ground controlled approach style)