Also, of those companies, most have contributed specifications (Microsoft, Cisco, Yahoo), and one contributed code (Google, with the initial version of Maps). All of that code is now under Apple's control, and if Apple needs to fix it or update it or debug it they can do so.
Flash, on the other hand, is closed-source. Adobe could, at best, provide Apple with a binary plugin to drop in. Apple would not be able to fix any bugs or track down any problems, and judging from their performance on OS X, it would be the source of a lot of crashes Apple couldn't do anything about. Apple might announce iOS 5.0 in June, a few days before or after Flash 11 comes out. Now what does Apple do? Rush to incorporate a major version change into a minor version release? Hold off on releasing until Adobe can get them a stable version? What if it's buggy? Now users who bought a new iPhone with iOS5, or users who updated to iOS5, think that Apple's released a buggy release, when in reality they've released a (probably good) release with a crappy version of Flash. This is exactly what happened with Snow Leopard already, and Apple caught flak for distributing buggy software because Adobe had released security fixes after SL went gold.
It's not about control, but determination. Adobe for years hasn't been able to show off a stable, reliable, and performant release, and so in exchange for Apple accepting Adobe's crappy code into the OS, Apple would also lose the ability to speak for the quality of the OS and experience as a whole. It's lose-lose for Apple, so where's the incentive? They got screwed with Snow Leopard, they'd get screwed with iOS, and in the end the ones who suffer are the end users, who can either wonder why their browser is so slow/crashy/laggy/jittery when scrolling, or who can wonder why they don't have Flash, but then shrug it off because most sites don't need it.
Flash, on the other hand, is closed-source. Adobe could, at best, provide Apple with a binary plugin to drop in. Apple would not be able to fix any bugs or track down any problems, and judging from their performance on OS X, it would be the source of a lot of crashes Apple couldn't do anything about. Apple might announce iOS 5.0 in June, a few days before or after Flash 11 comes out. Now what does Apple do? Rush to incorporate a major version change into a minor version release? Hold off on releasing until Adobe can get them a stable version? What if it's buggy? Now users who bought a new iPhone with iOS5, or users who updated to iOS5, think that Apple's released a buggy release, when in reality they've released a (probably good) release with a crappy version of Flash. This is exactly what happened with Snow Leopard already, and Apple caught flak for distributing buggy software because Adobe had released security fixes after SL went gold.
It's not about control, but determination. Adobe for years hasn't been able to show off a stable, reliable, and performant release, and so in exchange for Apple accepting Adobe's crappy code into the OS, Apple would also lose the ability to speak for the quality of the OS and experience as a whole. It's lose-lose for Apple, so where's the incentive? They got screwed with Snow Leopard, they'd get screwed with iOS, and in the end the ones who suffer are the end users, who can either wonder why their browser is so slow/crashy/laggy/jittery when scrolling, or who can wonder why they don't have Flash, but then shrug it off because most sites don't need it.