I generally get passed so I am usually flipping between views so I can see where the rider is behind me and then look forward to see where I’m going. It would be nice if there was a “only when pushed” button that allowed me to look back. I’m thinking like a car video game where you push a button and you have the view to the back, you let go and you return to your normal view.
For me I’d want something like this on my phone, not necessarily have it as a keyboard function.