Well, if John Gruber is right, now I get it.
On his blog Daring Fireball, he continues his two-year conversation on the subject.
The reason sounds logical knowing what perfectionists the folks at Apple are, being so manic about design, usability and performance: if Flash underperforms, they won't be able to fix it, as Apple controls the entire source code of the iPhone operating system (hence, the iPad, too).
And then there's Brian Chen's point of view from Wired Magazine's "Gadget Lab," where it's all about not giving away any piece of the profit pie.
"Allowing Flash -- which is a development platform of it's own -- would just be too dangerous for Apple," Chen says. It could be devastating to the App Store business model.
For Chen's host of reasons, many focusing on the business proposition, it's worth the fast read.