That is a horrible example: a physical product that was assembled by third-world clock-punchers in mind-numbing, depressing factories.
The impression I get will be they wont leave until the job is done to perfection. Not though the workers choice.
Passionate people might have lead the iPhone project, but there were assuredly many, many clock-punchers implementing the massive set of standard libraries available on the platform, writing specs and documentation, creating visual assets, sounds, etc.
I wonder how many left the project after launch because they were burnt out? I wonder if we would have a better product now if the core team has stuck around. Talent retainment isn't just about throwing more money at people, it's about a good working environment and often hours.