A lot of people have no idea you can take a photo with the volume buttons. I frequently see people struggling to take selfies with the touchscreen button.

I find it easier to take selfies with the onscreen button, as I can hold the phone from the bottom where i'm not likely to cover up the camera. It's awkward (with my hands and my 7+) to hold the phone in such a way that a) it's pointed at me, b) I have the volume buttons under a finger/thumb, and c) I'm not blocking the front camera in any way...