It does seem like a lost opportunity to do some outreach though. It's not hard to provide streams both in HLS and DASH, and streaming the developer conference to everyone could surely attract new developers to their platform (and not only developers, the same thing applies to presentations of new devices and consumer software).
To me it really looks like a statement against people without macs; Apple doesn't care about them, not even in its own interest of making money. They won't speak to you as long as you don't have an iDevice, full stop.
All computer ecosystems up to the late 90's were like that, the only thing special about Apple is that they are the surviving ones from those days.
It were IBM "mistakes" that made the PC different from all other computer eco-systems, however the current trends of commodity hardware and race to bottom prices are making PC OEMs go back to the 80-90's full integration of hardware/software culture.
To me it really looks like a statement against people without macs; Apple doesn't care about them, not even in its own interest of making money. They won't speak to you as long as you don't have an iDevice, full stop.