As ImprobableValue points out, the hardware mute switch on iPhone is an underrated, but highly convenient feature. Most of us on iOS might not realize it, but almost all Android devices are missing such a switch. OnePlus is the only major Android OEM to include it, meaning Samsung, Google, LG, and other major manufacturers omit it.
For those who keep their phones perpetually on silent, you might not see what a big deal this is. Having a physical switch with a color indicator makes it easy to tell whether your iPhone is going to ruin that meeting or not, without needing to actually wake up your device. You can flick the switch in your pocket, for example, until you feel the vibration, and know everything is going to be quiet from here on out.