Simulators are only meant for quick debugging, and both Apple and Google recommends testing on real devices. Therefore, it is imperative that developers test their applications on real iOS and Android devices.
In a fragmented market, constant device upgrades, endless iOS, Android versions and form factors make this task difficult. It is seemingly impossible to collect the necessary devices. Instead, use TestGrid.io's device lab.
With more than few 100 iOS and Android devices covering all popular form factors, we are always expanding our lab.