Making Microsoft look good
While I actually agree with Steve Jobs that Flash is a pile of crap, and the sooner it dies and is replaced by HTML5 the better, this kind of wide ranging draconian diktat is just making his company look worse and worse every day. Microsoft seem downright friendly these days in comparison.
Jobs is setting up Apple for a big fall somewhere along the line. The competition is catching up, or has done already, on the technical front, and in the end just being shiny and Apple-branded won't be enough when there are better and more open alternatives out there. Apple are now reacting instead of innovating, the multi-tasking change in OS 4.0 was forced on them because people now look at Android phones and ask why can't the iPhone do this. Which of course it could have long ago, but Jobs didn't want it to, so that was that.
It's a shame that Jobs' personality is the way it is. No-one can deny that when Apple are at the top of their game they can make some fantastic gear that people really want to use. If only he wasn't quite such a control freak.