Why Apple has no reason to make a 5" iPhone (iPhone 5, get it?)

After reading dozens of posts, both professional and otherwise about how Apple Needs to make a 5" iPhone, I thought I'd through my hat into the ring and give my personal opinion. Some of my points have been made before,

1. The need to have enough market pressure to do it, meaning they have to see a decrease in iPhone sales because people want larger phones

2. They would need to create an entirely new version of iOS. One of the nice things about ‘phablets’ like the note is software that is made for a larger screen (snote). An iPad UI scaled down would be impossible to use, and an iPhone UI scaled up gives you no new functionality, so an entirely different 3rd UI would have to be designed

3. Apple would have to release a 3rd SDK for devs to write apps for this new UI.If this new 5" phone existed, running scaled up 4" apps would add no new functionality.

4. Finally, Apple would have to actually produce this phone, and for it to have a similar ppi and build quality as the phone 5, and if Apple wanted to keep the profit margins of this device similar to that of the iPhone 5 they would have to charge about 100-150 more for it, which would mean it would likely do far worse then a 4" iphone commercially. This would result in smaller scale production, which in turn would make the device even more expensive to make.

In conclusion, this would create ALOT of fragmentation within the iOS ecosystem, and production of a different larger iphone would decrease Apple's profit margins. I think that if apple created a 3rd platform for iOS developers to develop for it would actually harm the amazing ecosystem iPhone users experience today. Apple has literally no reason to make a 5" iPhone, expect to humor the vocal minority that demands it. As we all know, apple prefers to tell us what we want than to ask us. Its got them this far.