While most people will probably end up installing Flash on their own, it will require some work.
On one hand, Apple is therefore doing its customers a disservice. On the other, given how slow and flaky Flash is on Macs, Apple may actually be doing them a favour.
Apple’s official reasoning, according to Engadget, is that “the best way for users to always have the most up to date and secure version is to download it directly from Adobe.”
But it’s hard to see this as anything more than Apple’s continued campaign against Flash, in favour of HTML5 for video and animation.