That's a design decision. Apple doesn't trust developers in general not to abuse this background API. They expect lots of aid requesting it, unknowledgeable users granting it without thinking much, and iPhones getting a crappy reputation for battery performance as a result.
I dislike this decision (taking a choice away from the user) but from a business point of view it makes sense.
I dislike this decision (taking a choice away from the user) but from a business point of view it makes sense.