I don't really feel like I need a dedicated physical camera button. I can always use the timer for selfies and group photos. My phone even uses the rear-mounted fingerprint scanner as a makeshift shutter button if the on-screen button is difficult to reach. Considering how many (all?) phones don't have an optically stabilised front camera, having a dedicated physical camera button might cause a lot of shaky photos as you try to press the button with the same hand you're holding the phone with.