Many folks underestimate the importance of a conductor in an orchestra. Sure, he's there to start and stop everyone, but there is a lot of music which has no definable beat being heard, yet, it is written in time. Everyone depends on the conductor to display where that time occurs. Without him/her it would be chaos. Plus, at times when time and tempo changes the conductor is indispensable.
In an orchestra ... if you happen to see a quatuor or any type of small ensemble, they doesn't have a conductor, nor a drummer nor a metronome.