What is the purpose of a musical conductor?

I don't understand the purpose of a conductor. I've seen them perform in numerous operas, symphonies, etc. If any of the players have any skill at all, they can keep the beat by themselves... or at the very least there can be an automated metronome to replace the human version. Are conductors only there for show (now-a-days)? Because they don't seem to have any use anymore, and they make more money than the ones with the real talent.