iOS still shines fit on device testing - you can conceivable have a representative sample of all iOS devices that your app should run on. I would probably want to have an SE, a 7s, and 8 plus and a X on the iPhone side and be okay with just one 9.7 inch iPad.

Solo developers, product leads and testers tend to choose the real device as their first destination. Linear coders and logic writers usually choose emulator.

Add a device variety testing. It's very hard to do right without emulator. Having all those device variations in physical form may be expensive and consume a lot of space.

My first job as a mobile developer was writing Windows Mobile apps for ruggedized devices. We had to test our apps outside with gloves on to make sure that the interface was usable by the field techs in the middle of the winter even if they lost their stylus.