Without quality development tools there are no quality apps, without quality apps there are no quality users, and without quality users the developers will flee. A simulator that runs headless as part of the normal build means your build can run these tests no differently than it compiles the Java sources. The lack of an emulated architecture layer, the overhead of a whole OS running, and the need for build steps like packaging (more on that to follow) means you are able to develop and deploy at a speed which just isn't possible in the current setup.