As a kid, I just assumed it was aesthetic. Like, someone for an audience of non-musicians to project themselves on to.
As an adult, I recognize that this is almost certainly not the case. Presumably the conductor plays a role that is necessary and helpful to the rest of the orchestra… but I’ll be damned if I can’t quite figure out what that is. Surely its not just timing? Can’t the players just… listen to one another to work that out?
That’s because the conductor plays an instrument, not a function, lad: a short, thin stick. You can hear it tapping if the music calls for it, for example it’s likely to be used when a flutist has dozed off and missed their entrance.