Well storyboards are declarative if you view the source but they're burdened with a ton of legacy. If a view is constrained by auto layouts the frame values should disappear but they don't, leading to a ton of false positives when committing changes. You only have cryptic ID's not real names as references. Also making a mistake in the XML format tends to crash the parser without giving a usable clue to what went wrong.

Last problem is that everything in Interface Builder still lives apart from the code. I think in Android everything gets compiled and is safe to use from there, with IBOutlets you're always either taking the risk (!) or dealing with optionals everywhere (?)