iOS is so huge you basically have to support their closed codecs, interfaces, and such.
HTTP Live Streaming and h.264 are standards. If anything, at most the use of them requires licensing fees and such. It's more appropriate to call them "not free" rather than "closed" since "closed" implies that they are not open for implementation elsewhere, which is not true.
For instance, Honeycomb also supports HTTP Live Streaming, and this move from Adobe would also benefit Honeycomb tablets down the line where Flash can be ditched for performance and integrity purposes.
Other than that, how iOS is executed by Apple doesn't really concern how content providers should serve their swag and how consumers can "properly" consume them. Adobe adopting HTTP Live Streaming opens up a door for content providers, and an untapped portion of the market is now open up to them. As for consumers, those who chose not to enable Flash for whatever reason (battery life, for instance?) now has a choice.
It's a win/win situation either way. This doesn't concern Apple one bit, but it does concern their user base.