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?
When I had parts in an orchestra, there were parts where i was supposed to just be quiet for a hundred bars or whatever. Far too long to count, and when youre sitting in your section you only hear the people next to you so i never knew what part of the song we were in. The conductor usually gives a signal when its time to start playing again, even If its just a nod or a look.