User experience? Developers do profiling, optimization, and the like all the time to make their apps smoother, faster, and less intensive on the system.
If every app did this properly, the benefit is that when you really need absolute highest priority for a task, you might actually stand a chance of getting it if every other app isn't doing exactly the same thing. But tragedy of the commons and all that..
If every app did this properly, the benefit is that when you really need absolute highest priority for a task, you might actually stand a chance of getting it if every other app isn't doing exactly the same thing. But tragedy of the commons and all that..