Which icon does what, and where will the video end up so that it can be found again? Hampus Sethfors in an Axesslab article, uses the example of trying to download a TED Talk on a smart phone for viewing later. He explains why icons are ruining interfaces He argues icons need labels otherwise users give up after a few unsuccessful tries and become unsatisfied with the app. Sethfors says, “Icons are like abstract paintings. They get different meanings for different people. It’s all through the eyes of an observer. And that ambiguity is really exciting with art. But not so much in user interfaces.” Saving space at the expense of usability is not the way to go. Sethfors also uses Instagram, Gmail, and Apple apps as examples of what not to do. He goes on to look at icons on a washing machine dial, and then to icons that really work. You can really see the difference.
People who design these things make a lot of assumptions about previous experience with instructions and ways of doing things.