Are You Avicii? Probably Not.
An Uber driver once gave me an analogy that described how he and most of his fellow Uber drivers felt about passengers who immediately reach for the aux cord after hopping in; 'It's like walking into someone's home, heading straight towards the speakers and plugging your playlist in.' If you want to listen to some of your own tunes, connect your Spotify through the app or ask politely if you can borrow the aux cord, but remember that you're in their world now. Please and thanks will take you a long way. Something to note is that aux cords and other charging accessories are not mandatory for UBER drivers to have so don't throw a shit fit if there isn't one available.