One of the coolest features about Android Auto is that if you have an Android smartphone, you can use it, regardless of whether or not you're using an Android Auto head unit in your vehicle. Simply open the Android Auto app and let your phone turn into the hub for your vehicle.
But like all cool Google features, this one's also being discontinued.
Android Auto just received a pretty big overhaul on dedicated receivers and head units, so the platform itself is still in a healthy place. But during Google I/O 2019, Google showed off a new, dedicated Google Assistant experience for the road, and that's going to be their focus going forward.
And this move honestly does make a lot of sense. It's not a scaled down version of the big, real Android Auto interface. Assistant for the car gives drivers a streamlined and focused feed of things like navigation and music control on their phone that can all be voice-controlled, and it's built around a phone form factor instead of trying to make a stereo OS work on a 5-inch screen.
Expect this change to happen over the summer.
source: 9to5Google
Android Auto on the phone is a mixed thing. It’s great to have it but is also kinda clunky to use, especially on smaller phones. I’m happy they have streamlined it to essentially a Google Assistant for driving. The real thing on car consoles looks much, much better and would not translate well to smaller screens at all.