Reference counting has an incremental performance burden because of predictable object freeing, while garbage collection has a periodic pause. On mobile devices

Reference counting has an incremental performance burden because of predictable object freeing, while garbage collection has a periodic pause. On mobile devices you often must worry about response-times; it is a lot more easy to reason 'we need to ease up on such and such at this time', and be sure you solved the problem. Garbage collection pauses can be less straight-forward to tackle.