It's always interesting to me how simplistic significant changes to a product seem to outsiders. "Overnight" was the key word here. What most people don't consider is that the UI may need to undergo a serious revamp (with nearly unlimited possibilities to evaluate in order to find what Apple's design team believes best), the testing that QA has to perform to catch edge case bugs from the revision, not to mention that these changes may only be deliverable through an update to iOS itself (something that is already considered to be an unwelcome burden by some users).

If you don't think that Apple and its competitors genuinely want to deliver the best experience that they can within the time and cost budgets that they have to adhere to if they want to remain competitive then you severely underestimate the people who put in the long hours required to get these products into your hands.