iPhones have always had a switch that toggles the phone between mute and sound on. This button replaces that switch

Sorry, in advance, for the long, descriptive post, but the value of a dedicate, slide mute switch is somewhat nuanced.

The mute switch on an iPhone is a physical slide switch. Without looking, you can feel if it's muted (back) or active (front) position. Alternately, you can see the condition as, when it's in the "mute" position, it has an exposed orange (painted) indicator. Neither of these verifications require that the phone be awake or to light up the screen. It can also be activated with the device off, so that if you turn the phone on in a quiet place you don't have to wait for the UI to become responsive (usually after start notifications have actuated, which occur before software buttons can be pressed to mute the phone). It is a single action to mute, compared to a 5 gesture sequence to silence the phones primary sounds (which can be ringtone OR playback volume, but not both) and an 6-8 gesture sequence (depending on the wake-status of the last used app) to silence the secondary phone sound. Note: I'm assuming that face unlock is active and you are staring at your phone obtrusively; entry of the unlock code would add 7-9 additional touch gestures.

While I agree that a button is nice, it still takes at least two actions - press the button and visually confirm its actuation puts it into the desired mode. There are times when you are unsure what mode the phone is in. On an iPhone, that is not visible from any screen until you either a) wake the phone and actuate a volume button (neither visual nor haptic feedback occurs when a volume button is pressed) or are logged into the phone (two minimum gestures plus face authorization) and use the action center (swipe function) to visually verify th volume position.

Now, you could easily argue that this is fucking terrible UI design, and I would 100% agree with you. I would, likewise agree, that most technical features on an iPhone are certifiably obtuse - ex: you cannot turn on your hotspot without entering the settings app; it's not even an action center icon option as it is on Android. I would add that it's also monumental dumbfuckery that your hotspot is the name of your phone and cannot be changed. Or that there is no function to alter the Prompt volume in the phone (ie. for GPS directions) unless the prompt audio is actively playing - difficult if the prompt volume is accidentally (or temporarily) set to zero. In 3rd party apps the prompt volume is several menus deep; for the OEM map application, it doesn't exist - there is literally no setting.

But, it remains - if you want to mute the alerts on your phone, the switch requires fewer actions and zero view of the device to actuate, and zero activation of the screen or login to verify it's condition. You may never need to discretely silence your phone or check that it is in silent mode without taking the phone out and unlocking it, but many of us find it quite useful.

I mean TVs have volume buttons but also a mute. It's nice to be able to use volume to set a specific level but then also quickly toggle between that perfect level and silent.

It's not something you strictly need a physical button for, but the way they implemented it on old iPhones was nice. It was a physical switch rather than a button, and it looked different in the two positions--the slider under the switch was red on one side and black on the other. (or maybe silver, i forget, but it didn't stand out the way the red did.) So you could tell at a glance if it was muted as well without turning on the screen.

The new button seems like a step back from that to me, but if you don't use the silencing feature then a reprogrammable button is maybe more useful to you.

The iPhone has volume buttons as well but the mute switch was a way to quickly mute your notifications completely. Its honestly the one thing I miss about having an iPhone.