On a computer, having 2 screens means having additional real estate when arranging windows and doing work while multitasking. Little to nothing on phones or tablets is designed specifically with multitasking in mind. I don’t use my iPad’s multitasking features because I find them distracting. Much the same way I found Picture In Picture displays on old CRT TVs distracting.
I’m reminded of the Nintendo DS I owned years ago. The top screen was where the action happened and the bottom was almost always used for inventory/status/other static displays. If it weren’t for the fact that the bottom screen was touch sensitive, it would have been a waste. I’m sure there were games that utilized both screens equally effectively but I never came across any.
Spotify in the Surface Duo screenshot above is doing the same thing as the bottom screen in the Nintendo DS - just showing something relatively static that I don’t really need in the moment. If I DID need it in a moment, there’s a shortcut to get to it (Control Center on an iPhone, a pause menu on a game console).
I’m ignoring in all the above that many people pay attention to multiple screens all the time via using an ipad while watching TV or what have you. In those circumstances though the focus is very separate - it’s not two screens immediately next to one another fighting for focus. Unlike Picture in Picture its easy to divide attention between the two and hop from one to another at will. I guess you could watch a movie on one screen of the Duo while browsing twitter on the other but is it worth buying a single $1400 device for just that? When you probably have a TV, tablet, laptop, and phone already?
TL;DR: Developers may very well one day figure out a way to use a second phone/tablet screen effectively but for now it’s just a distracting gimmick that doesn’t seem to increase functionality.
