Unintentional black bars on the sides on Android

I am currently making a 2D game with 9:16 aspect ratio in mind. The camera size is set to 9.6 and the game view covers the entire background (resolution of the background in 1080x1920). But when I build and run the game on Android there are black bars on the sides. I was wondering why this would happen? I tested on a tablet and phone with resolutions 720x1280 and I assumed since the aspect ratio of both the devices is 9:16 there wouldn't be any black bars.

 

I realized that because of the virtual buttons on Android, I had to change the aspect ratio in the editor to 16:10 for the black bars to disappear