This is just how I think about user interfaces in general. I think developers and engineers should make the effort to create a zero resistance experience for the end user. In most other aspects of life, tools and appliances are easy to use. In computing, interestingly the only apps that come close to being as intuitive as they should be imo are games. Most user interfaces for computer hardware and software are absolutely terrible, and you can tell by how it alienates large portions of the population. Apple user interfaces are are generally not anywhere near as terrible, they are generally fairly good. Which can probably be said for the touch bar volume control... people do indeed manage to change the volume without much instruction, but that hold-and-slide thing is generally something that people don't know. Another thing is gestures, both in iOS and macOS. You'd think that they're great, but without instruction most people are actually not going to end up using the majority of them. Simply because they don't know that they exist. In my opinion, when that happens, the user interface isn't delivering the best possible experience. It may well be that we don't know of any better method in some cases, but for volume control we most certainly do.